The existing reviews seem to assume familiarity with the series, so I'll try to provide a little more background for anyone considering dipping a toe in the water for the first time.
This is, I think, the thirteenth novel (as against the fourteenth, suggested in another review) in the series known as 'The Fethering Mysteries'. Fethering is a fictional small town near the West Sussex coast, presumably somewhere in the Chichester - Arundel area; it's decidedly conservative (with whichever size 'C' you care to choose) and suffers an alarmingly high rate of criminally induced mortality. The local police are, shall we say, rather pedestrian, but this deficiency is amply counterbalanced by our doughty heroines, the unlikely pairing of Carole Seddon, deeply conditioned by her instinctively disapproving middle-class upbringing, and her neighbour Jude, a comfortable, earth-mother figure who oozes pragmatism and practices as a healer. The vague air of mystery surrounding Jude is underscored by the almost complete absence of any reference to her surname.
Carole and Jude coduct their case-conferences in the Crown and Anchor, over large glasses of Chilean Chardonnay. If the alliteration in that sentence seems a little over the top, it's worth noting that alliterative titles are a hallmark of the series - recent examples include 'Blood at the Bookies', 'The Poisoning in the Pub', 'The Shooting in the Shop' and 'Bones under the Beach Hut'.
In the current volume, the tale centres around the Whittaker family, 1990s dot.com millionaires. Ned and Sheena have bought the nearby Butterwick Estate, where they enjoy a life of luxury, accompanied intermittently by one or both of their flavoursome daughters, Fennel and Chervil. Fennel, the elder, is a talented artist but suffers severely from lifelong problems with depression; Chervil sees herself as a mover and shaker, and is currently developing part of the estate as a 'glamping' site - glamorous camping, living in spacious Mongolian yurts with most of the facilities of a luxury hotel conveniently available on-site. (This idea is by no means fanciful - just check 'yurt' on Google!). She seems resentful of the extra attention Fennel receives because of her medical problems. Chervil's current boyfriend, Giles Green, is the son of the owner of Fethering's Cornelian Gallery, which is currently hosting an exhibition entitled 'Gun Culture', by the somewhat off-putting 'conceptual' artist Denzil Willoughby - hence the title of the book. Life in Fethering is never simple, and the tale develops entertainingly until Fennel is discovered in one of the newly-built yurts, having apparently committed suicide - but has she, or is there a more sinister explanation?
In view of Fennel's past history, the police appear happy to take the situation at face value, but Carole and Jude are not convinced. In due course the mystery is resolved; the plotting is scrupulously fair to the reader, and there are sufficient clues to allow the puzzle to be solved correctly - but of course you won't realise this until you've put your money on the wrong horse, and there are lots of horses in the race!
Simon Brett is an experienced and skilful writer. The Fethering novels represent only part of his output, and most readers would, I think, agree that the series is intriguing and enjoyable, if not particularly demanding. Most of his work, including all the 'Fethering' books, is broadly within the Christie mould, set in an England suffused with warmth and tradition which neither exists nor ever did exist away from the pages of fiction. My personal view is that the earlier Fethering novels are the best, but they are all good; I wouldn't hesitate to recommend any crime buff to sample a few. On the downside, though, the formula tends to create an impression of repetition, almost of deja-vu, which suggests that it may be time for the series to be drawn to a conclusion.
I generally prefer my crime fiction to be credible, though that is not necessarily a synonym for realistic. Like Christie's Miss Marple stories, the Fethering novels struggle to qualify as credible, and they are certainly not realistic. This is particularly evident in the way Carole and Jude succeed in extracting vast amounts of personal information from characters who are under no obligation to tolerate their unofficial snooping. Despite this, there is something about Simon Brett's writing which encourages the reader to suspend normal preferences and to curl up for a cosy and undemanding wallow in nostalgia.
In summary, if you are new to the Fethering mysteries, and you're not looking for gritty realism, I have no hesitation in recommending that you try 'Guns in the Gallery' or one of the other Fethering novels. Those already committed to the series have no doubt already greeted the latest addition with glee in the greengrocers and cheering in the chip-shop, and who am I to argue? For the remainder, who have read one or two of the earlier books, you know what to expect and you probably won't be disappointed - but don't anticipate any exciting new departures.