Channel 4 have managed a nice line in cult comedy series in recent years, which despite a consistently high quality have not always found the audience they deserve. Everyone I know watched Father Ted, a good many of them were into Black Books and Spaced, but less than half were even aware of The Book Group. Maybe it hasn't had time to build up the right word-of-mouth (it is the most recent of the above mentioned series) or maybe it lacks that all-important 'hook' that snares an audience, whether it be the engagingly daft priests in Father Ted, the Basil Fawlty-like rudeness of Bernard Black, or the identifiably sympathetic leads and media-aware hipness of Spaced; all of these programmes had a key element that rapidly became the signature of the individual series. On top of that, Father Ted wandered confidently into the realms of the surreal, Spaced had its post-modernist film referencing and directoral inventiveness, and Black Books had a heightened, absurdist sense of unreality. Most of all, each of the series boasted easily likeable characters – even Bernard Black is rude in a funny way, a manifestation of a personality trait that almost all of us keep firmly under control but would love to occasionally let rip.

The first thing that strikes you about The Book Group is that it has none of these. Not one of the characters are instantly likeable and a couple are genuinely unpleasant. There is no surrealism, no post-modernist referencing, no wildly comedic characterisations or laugh-out-loud gags. No single character is given more screen time than another and the direction is decidedly low-key – right from the start this plays more like drama than comedy. Early laughs are awkward ones, coming at the expense of characters' sometimes acute embarrassment. And if that wasn't enough, the entire first episode takes place in the here and now in a single location, most of it in one room. So what is it, exactly, that makes The Book Group so damned good?

The first response has to be precisely because it is so unlike its quoted comedy predecessors. Like BBC's The Office, it is something of an observational work, a comedy of embarrassment (though I have yet to warm to The Office, which seems to recycle the same jokes and situations but narratively go nowhere) and could indeed wear the jacket of comedy-drama without inviting a visit from the fraud squad. As writer-director Annie Griffin states on the commentary track, a character doesn't necessarily have to be likeable to engage our sympathies and this seems to be the challenge she sets herself – to create situations in which an audience can warm to characters that on the surface you'd actually like to slap.

Central to the narrative (though not in the traditional sense a main character) is Clare, an American living alone in Glasgow who has the idea of starting a book group in order to meet like-minded people. To her surprise and dismay, her advertisement is answered not by the hoped-for intellectuals, but quiet, handsome, wheelchair-bound Kenny, football obsessed Rab, Scottish, Dutch and Swedish football wives Janice, Fist and Dirka, and good-looking but opinionated young Barney. Only Barney meets her expectations and it is perhaps appropriate that he is every bit as insufferable as her. Both are self-obsessed: Clare is wallowing in self-pity and has a condescending attitude to just about everybody, while Barney is a smugly pretentious posh boy who believes he is intellectually superior to most of the human race. Actually connecting with the football wives on any level is initially tricky, and it is uncertain whether Rab has ever even read a book, his motives for even attending the group being at first strangely uncertain. The only really sympathetic character in the first episode is Kenny, a genuinely nice guy who still manages to kick against expectations with his almost vicious reaction to an aggressive come-on in episode 2, and there's always that nagging concern that we're sympathising with him because he's the one in the wheelchair. Despite its restrictive setting, its sometimes wincingly irritating character details and a lean towards the dramatic, the first episode somehow grabs through a combination of intrigue, decent writing, nicely judged performances and oddball character details. It also ends on one of the best examples of comedy of embarrassment I've seen in years, which I won't spoil for the uninitiated.

Having established the format, the surprise is that in episode 2 the show opens up considerably, showing us the characters in their work and home environments and expanding on elements only hinted at in the first show. Episode 3 even begins with two fantasy sequences, dramatic realisations of the books Clare and Kenny have begun writing. As the series progresses, Griffin's aim of making us care for people we wouldn't want to actually spend time with ourselves is successfully achieved, in the main because we learn why the characters behave the way they do. This doesn't always make them likeable, but they do become more human, oddly believable and, well, interesting. And by the end of the series, it's hard not to warm to all of them on some level. They become like flawed friends, people we like but wish they would just stop being so... well, you can fill in your own irritating personal trait here.

Once the attachment is formed we care about them, laugh with them and sometimes at them. A second viewing can actually prove even funnier, as familiarity with the characters reveals just how effective the balance between drama and comedy actually is and how well both elements work. It's this that really makes it part company with the aforementioned The Office, most of whose characters never really become either sympathetic or remotely likeable; the squirm factor here is actually used to develop narrative, character and audience identification.

Each episode is built around a different meeting of the group – whoever selects the book is obliged to host the meeting, which proves a useful dramatic inroad to that character's life and their relationships with those around them. In almost all cases personal relationships are to some degree in trouble and all of the characters are chasing a need, and not always an obvious one. Some of these are met, but even when they are the results are often unexpected. One of the series' real strengths is its refusal to play narrative by numbers, in part because the characters themselves avoid following traditional dramatic or even comedic paths; even though they do all go through the expected transition almost demanded by filmic storytelling, they do not necessarily find the sort of resolution so many movies (and even TV series) have led us to expect.

Writing and direction aside, the key to selling this lies in the performances, with all of the relatively unknown actors completely inhabiting their roles and creating fully rounded characters that are realistic but with that slightly exaggerated comedic edge. Rory McCann in particular makes for a thoroughly engaging Kenny, caught between his desires and frustrations, and trapped between his fantasies and reality. And should anyone suggest that James Lance is overdoing it as Barney then I can assure you otherwise – every town and city has a whole breed of such twerps, and the character's sometimes uncanny resemblance to the room-clearingly insufferable boyfriend of a past friend of mine actually convinced me that he was based directly on him.

The menus are attractively presented, a well-done computer animation of a book opening to reveal the main options, with selections prompting a few more pages to fold over to the chosen sub-menu. The downside is that the commentary track cannot be accessed while the programme itself is playing, and if you want to just dip into the commentary it's a bit of a trawl through the menu system to activate it and return to your chosen spot, especially as the episodes themselves have no chapter stops.

An anamorphic 16:9 transfer that is typical of VCI's work in this area in many ways, though somehow doesn't seem quite as obviously dynamic as the same company's excellent job on Black Books. This could partly be to do with the visual aesthetics of the series itself, with its emphasis on naturalistic lighting and settings rather than the more studio look of Bernard Black's shop. Still a very decent job, with solid blacks, natural-looking colours and no sign of artefacting or edge enhancement, and played on an LCD monitor at work it looked seriously impressive.

The Dolby 2.0 soundtrack does the job fine, this being a long way from an action piece with even music kept to a minimum. Dialogue is key and always comes across clearly. Pleasingly, there is no laughter track – this is not gag-based comedy and this would have been completely inappropriate, completely undermining the dramatic elements of the show.

The best extra here has to be the Commentary Track by writer-director Annie Griffin. An American who has for some years been resident in Glasgow, she has a good speaking voice and plenty to say and her delivery is very nicely paced. Despite covering all six episodes, quiet spots are extremely rare, and I for one found Griffin's verbal contribution almost as fascinating as the episodes she was commenting on. Much of it is surprising and entertaining: Kenny's nervousness in episode 1 was in part the result of Rory McCann's utter terror at acting before a camera for the first time; Griffin's desire to create in Clare "an obnoxious American," despite hailing from the same country, and her irritation at the way American visitors to Glasgow arrogantly try to correct locals on their pronunciation; her hilariously deadpan analysis of a scene in episode 3 which a particularly strong swear word is repeatedly used – "You just cannot say 'cunt' before 10.00 in Great Britain." A fine commentary.

There are over 17 minutes of Interviews with cast members. Though there is the inevitable back-slapping and admiration for colleagues and the script, this is far more insightful than the usual EPK and supplies some useful background detail on the characters and some engaging behind-the-scenes stories, plus the occasional amusing titbit – Saskia Mulder admitting, for example, with a very telling look, that she loved playing a character who was in love with Kenny. Some information is repeated from the commentary, but it's nice to hear the story of Rory McCann's extreme nervousness from the man himself. Framed at 4:3, the interviews are mostly well lit and very nicely presented. They also do not have the usual DV look – whether this is the result of shooting on film or some careful post-production filtering is uncertain, but the results are very pleasing.

Finally there is a transcript of a live Internet Chat conducted with Annie Griffin just after the last episode of the series had aired for the first time. Though brief, it's still a useful read, not least for the participant who felt that the horrible Barney was far and away the most interesting and emotionally together character in the series. Now I think I know who that might have been....

As mentioned before, there are no chapter stops in the episodes themselves, which is a bit of a pest, but at least tolerable on a 22 minute programme. Subtitles are English for the the hard of hearing only.

The Book Group deserves to be more widely seen. In just one episode it carves its own unique identity and over the course of six creates fully rounded, wonderfully performed, not obviously likeable but still sympathetic characters and develops them in interesting, not always expected ways, all the while managing to stay rooted in a reality. I have yet to catch series 2, and it will be interesting to see if it goes the way of the second series of Spaced (every bit as good) or Black Books (loses it completely) or ends up somewhere in between. On the basis of this fine first series, I'm hoping for the first.