Meddling with the novels of such a geek luminary as Douglas Adams is a precarious business, so it's no surprise that this reworking of his Dirk Gently's Holistic Detective Agency - first shown on BBC4 last December - had ardent fans up in arms over the deviation from its source novel. But a series has been commissioned, so all their favourite bits of the books have a chance to make it to the screen. For the rest of us there is enough to appreciate in a plot that expands from a case of a missing cat to some surreal flights of fancy. Stephen Mangan is great as the chaotic, evasive Gently, while Darren Boyd does a great line in bewilderment as an unwitting sidekick.

Stephen Mangan's not-great-but-better-than-expected turn as Douglas Adams's holistic detective actually stands up to a second viewing, so even if you watched it on BBC4, you may be surprised to find you like it more this time around.

Fans of Douglas Adams were unimpressed with this reworking of his Dirk Gently's Holistic Detective Agency when it aired on BBC Four last year - they felt it deviated too far from Adams's original novel. Tonight, it gets its first terrestrial airing with the detective (Stephen Mangan) examining a case that links a missing cat with an exploding warehouse.

I like comedies, I like dramas. Comedy-dramas I've never been sure about and Dirk Gently has all but convinced me they don't work. The eponymous hero is a detective who believes in "the fundamental interconnectedness of all things" but after this outing, even he'd struggle to make a case for that hyphen straddling the two genres.

Gently is the creation of Douglas Adams who was working on another of his cases when he died. This one began with a missing cat and ended with what seemed like the attempted murder of the three attractive leads, Stephen Mangan as Gently, Helen Baxendale and Darren Boyd, who was in the recent Whites with Alan Davies and seems to be cornering the market in sidekicks to curly-headed fools. They all survived but surely the show won't.

The soundtrack twanged with Randall & Hopkirk-esque harpsichord (or did that pair use a spinet?).

The hero chugged around in a Leyland Princess. But Dirk Gently lacked drama, despite blowing all of BBC4's special-effects budget for 2011 on a warehouse explosion, and it lacked comedy with not one halfway funny line - this only making me yearn for the return of Mangan's cFree Agents from last year and scour Amazon for a cheap box-set of Baxendale's Cardiac Arrest, deadly certain laughs of the darkest hue.

There was something satisfyingly leisurely about Dirk Gently, adapted from a Douglas Adams novel about an old lady's missing cat, and starring Stephen Mangan as the one-man "holistic detective agency" hired to find it. It wasn't the smoothest of narratives. I could never wholly applaud a plot that so late in the day relied on hypnosis and time travel (the only sci-fi trace element from the original story). And, although there was laughter and invention, I'm not sure that bumping into a closed door aspires to the heights of modern comedy, even when accompanied by the ditsy loose-limbed rhythms of 1950s jazz. But it had a pleasing, meandering pace to it. You had to admire the way that Dirk's investigative method - based on "the fundamental interconnectedness of all things" - made an unlikely virtue of stringing together unlikely coincidences. And Mangan did a fine job as the eponymous oddball loafer-genius, with his boffiny corkscrew hair, love of biscuits and the rapid eye movements of a man accustomed to making a quick buck and a quicker exit; Darren Boyd was good, too, as the bewildered but biddable sidekick Macduff. As the girlfriend, Helen Baxendale was as nice as ever. It wasn't Sherlock, but I wouldn't mind seeing what a series could do.

Dirk Gently, BBC4, Thursday

Douglas Adams' 1980s crime caper was set in the present, but you wouldn't know it from the jokes.

There's a lot missing from Dirk Gently (BBC4). I don't mean the missing cat that scatty and unconventional detective Dirk has been employed to find, or Gordon Way, the billionaire who disappeared at exactly the same time (though time is complicated around here). I'm talking about things in Douglas Adams's novel, vast swaths of it, in fact, that have gone missing in its transformation to the screen. Adams freaks (I think the f-word is justified here) will, no doubt, be cross.

Truth is, though, it would be physically impossible to cram all that wild imagination into 60 minutes of television. If it sounds as if I've read the book and know what the hell I'm talking about, then that's lovely, but misleading; I haven't, though I have spoken to someone who has and he reckons what we have here is the kernel of the book, a kind of digested-watch version of Dirk Gently's Holistic Detective Agency. And also that it captures its essence.

Coming to it fresh, it's a neat story about aforementioned missing cat and time travel, with a smattering of quantum physics and the fundamental connectedness of things. With a lovely performance from Doreen Mantle as the old lady/murderer. Stephen Mangan's good in the title role, too - a teeny bit irritating perhaps, but then Mangan is a teeny bit irritating. So is Dirk Gently, though - it's perfect. Funny too. Quite funny...

I have no idea how loyal the makers of BBC4's Dirk Gently were to Douglas Adams's Dirk Gently's Holistic Detective Agency, though I'd hazard a guess that a few liberties have been taken. The iPhones and Blackberrys were one giveaway; the various references to East 17 another. And, of course, the book's title has been truncated. Does it matter? Probably, to some of Adams's more devoted fans. In the context of last night's viewing, though, I'm inclined to think that for most of us it doesn't. Not a jot. Gently was so jolly, so rollickingly good natured, that to complain over such trivialities seems terribly poor form.

Gently is a detective. More than that: he is a holistic detective. He believes that everything is interconnected. And so when, on being hired to investigate the disappearance of an old lady's cat, he ran into an old friend from university, he was certain it was a clue. In a way, it was. The pair teamed up, tackling the triple mystery of Henry the cat's whereabouts, the departure of a businessman from a nearby warehouse, and the failing love life of MacDuff (the friend). What followed was a cartoonish series of escapades that saw Dirk prove his creativity, if not sleuthing skills, with his Scooby Doo-esque plans. He faked suicide to steal a set of psychiatric records, he hypnotised MacDuff to take him back in time (not literally, though there is some of that) and he pretended to be a patient at the practice of MacDuff's girlfriend. He found Henry, sort of - and a lot more besides. That nice old lady who hired him, for instance? Not quite as nice as she seemed.

Stephen Mangan - hitherto best known as Guy Secretan from Green Wing - was ideal casting as the hapless Dirk, and Darren Boyd just as perfect as MacDuff. Helen Baxendale, too, made a welcome return as MacDuff's disgruntled girlfriend. In fact, there wasn't very much you could fault about the production at all. Right down to the quirky camerawork and youthful, poppy soundtrack (who would have thought the Hoosiers could be so right in any situation?), the director, Damon Thomas, got it pretty spot-on. The result was a pleasingly festive-feeling adventure; part Wallace & Gromit, part Doctor Who, part The Secret Seven. And the best thing? There wasn't a Christmas tree in sight. Douglas Adams once claimed that Gently would make a better film character than his more famous hero, Arthur Dent. Based on last night's experience, he may well have been right.

Dirk Gently review

Overall, your reaction to Dirk Gently will largely depend on if you've read the source material. If you have, you'll perhaps be disappointed Overman's adaptation has gutted Adams's surrealism and rampant oddness.
But if you haven't, you'll probably be more accepting of another TV detective series with sharp writing, quick pace, imagination, fun performances, and a unique gimmick at its heart.