Ian Watson is facile and fecund. Ideas come so easily to him, and are scattered so profusely through his stories, that they can get in the way of storytelling. It is a trap he falls into all too often. He will start to tell one story, then when he gets bored bung in another idea that sends the whole thing shooting off in a completely different direction. It happens twice in "A Speaker for the Wooden Sea," for instance: this begins as the story of a sophisticated trickster arriving to con the natives of a backward planet and finding himself not up to dealing with their wiles; suddenly, just before the mid-point, it changes direction and turns into a maritime adventure out upon the wooden sea of the title; but despite the novelty of the setting, this does not hold Watson's attention for very long, because the story changes direction again, and becomes one about a computer achieving transcendence and the moral consequences for the humans affected by it. One, or possibly two, of these ideas thoroughly explored would have made a superb story, but they fit awkwardly together, fail to achieve a satisfactory resolution, and leave the reader disappointed. Similarly, Watson's homage to Jules Verne, "Giant Dwarfs," which recreates the journey to the centre of the Earth with Verne himself as a participant and a liberated young woman as narrator, manages to cram in troglodytes, Nazis, and a timeslip, which seems to be an idea or two too many.

Lack of resolution seems to be a consequence of Watson's facility with ideas; stories start with fascinating situations, but then run out of steam before the end, as if Watson has simply lost interest. In both "An Appeal to Adolf" and "Hijack Holiday" the narrator is simply killed before most of the plot strands have had a chance to be resolved. In "An Appeal to Adolf" the death is particularly ludicrous—the narrator is shot out of a cannon in his underwear—which does a disservice to the overly complex but thoughtful story that has preceded it, a story which involves an alleged gay relationship between Hitler and Ludwig Wittgenstein, and battleships so long that three alone are enough to bridge the English Channel.

Fortunately, if one idea doesn't work for you there are three or four more coming along in a minute, and these unsatisfactory stories are balanced by others which are more tightly focussed, and which work much better as a consequence. "The Black Wall of Jerusalem" seems like a prime candidate for Watson's over indulgence in ideas: a mysterious wall which appears and disappears in the older parts of Jerusalem becomes a portal to strange and threatening figures who might be pieces in a cosmic game. But by limiting the story to one man's frightening visit to this other world, and leaving so much of the game a mystery, Watson gives a powerful sense of coherence and unity to this vivid story.

The story notes tell us that when he began writing "A Free Man" Watson thought that it might be a novel; instead it has ended up as a thirty-page story and perhaps the best piece in this collection. The work involved in editing the story down, in cutting out extraneous detail, in concentrating on just the one idea, has paid dividends. This is about as controlled a piece of writing as you get from Watson: a man appears in Leamington Spa with no memory of who he might be, but with a healthy bank balance which keeps topping itself up to the same level no matter how much he spends. By keeping our interest solely on his quest to establish his own identity, we care more and discover more than we do with the less controlled, more scattergun approach elsewhere.

The quest for identity in "A Free Man" becomes closely tied to the protagonist's sexual relationship with a girl he meets. One of the less pleasing aspects of this collection is Watson's increasing and often perverse interest in sex, but here, for once, the sex and the story work together. At times, some of the stories, such as "An Appeal to Adolf," "Hijack Holiday," and "The Navigator's Tale," become exercises in prurience. Even if "Lover of Statues" doesn't quite manage to marry the enigmatic alien, who uses a Madrid statue as a sexual partner, with the narrator constantly harking back to her own failed relationship, it is still the best of these more sexual tales.

All told there are 17 stories in this new collection (accompanied by story notes which are excessively informative in some cases, mind-numbingly uninformative in others), of which three—"The Black Wall of Jerusalem," "A Free Man," and "One of Her Paths," which concerns the quantum effects of space travel when an entire ship's crew find themselves alone for the six months their vessel is in Q-Space—represent Watson at his very best, controlled, original, energetic, and entertaining. But these are offset by too many duds ("Barking Mad," a pastiche of Inspector Morse, seems particularly feeble to me), and a number of stories—"Lover of Statues"; "Separate Lives," about a couple who transgress sexual laws and find themselves exiled to different realities; "Starry Night," about a man transported to a world so far beyond the rim of our galaxy that he can have no hope of return; and "The Butterflies of Memory," in which mobile phones vampirically suck out our memories and replace them with false ones, confusing our sense of identity—which feel as if they need at least one more rewrite to tie the disparate ideas more closely together and make them work more coherently as stories.

Ian Watson is, as I said, facile and fecund. Which makes any collection of his stories a roller-coaster ride. There are good ideas galore, but they don't always make good stories. When they do the results are glorious; when they don't one is left with an unsatisfactory sense of a talent gone awry.

Paul Kincaid is the recipient of the SFRA's Thomas D. Clareson Award for Distinguished Service for 2006. He is the co-editor of The Arthur C. Clarke Award: A Critical Anthology.