Brasyl, by Ian McDonald

Brazil, 1732: in the Amazonian heat, Luis Quinn, a swordfighting Jesuit priest, makes a treacherous journey upriver to assassinate or recover a rogue member of his order. Brazil, 2006: Marcelina Hoffman, capoeirista, cokehead and aspirant TV producer, flits between editorial conferences, ayahuasca congragations and car chases in the growing certainty that her life is being hijacked by a Doppelgänger. Brazil, 2032: under the ever-circling satellite eyes of the Angels of Perpetual Surveillance, Edson Jesus Oliveira de Freitas, favela entrepreneur and occasional transvestite, falls in love with the operator of a mysterious travelling quantum computer – a woman who appears, additionally, to be able to resurrect herself.

These three narratives form the bulk of Brasyl, a flawed technicolour storm of a book by one of Britain's most consistently interesting SF writers. Ian McDonald's attention seems increasingly drawn to imagining the future world country by country: his Chaga books, written during the 1990s, drew teasing metaphorical parallels with colonialism in their description of a future Africa progressively engulfed by a terraforming alien technology, while River of Gods (2004) was set in a mid-21st-century India fractured by water wars and mass-entertained by Bollywood AIs. Like its predecessors, Brasyl is packed with deftly integrated research into the cultural and linguistic memes of its chosen territory (so much so that non-Portugese-speakers will welcome the glossary); like them, too, it inhabits the fuzzy territory at the limits of contemporary science where philosophy and research converge.

But Brasyl isn't as successful a novel as its forebears, and it manages this by the paradoxical (perhaps quantum) trick of being simultaneously too thin-spread and too focused. The book follows the fortunes of three separate narrators in three wildly distinct time-periods, so it's perhaps unavoidable that the segment of the narrative dealing with the present day should look a touch flat compared with the barbaric Fitzcarraldan sweep of the historic segments or the parched techno-glory of the future. But the problem bleeds into the 18th-century segment as well.

Anyone who's read a smattering of SF in the past decade or so may now feel rather tired by the technological possibilities of the Enlightenment – Neal Stephenson, for example, has wrung three huge novels out of the Baroque-naïve approach to information theory – and here we are again: no sooner do Quinn and his 18th-century philosopher pal take ship for the heart of darkness than one of them produces a prototype "Governing Engine" and kicks off a discussion about ones and zeroes. Even sentences like "I can see how it might be possible to use such a set of cards to play a program in a musical automaton" only go a little way to spoiling a brilliantly bizarre slice of imagined history that prefers to get its effects through characterisation than through period clichés. Or, at least, through characterisation and a floating painted war-church full of slaver priests.

The real problem with Brasyl lies in the strange lack of invention that it brings, late on, to a fascinatingly weird premise. This is mainly noticeable because invention is lavished with baroque excess on almost every incidental detail in the narrative: when it comes to the crux of the book, the reader is surprised to find all the dark narrative mutterings about quantum theory and the multi–verse boiling down, after some fairly obvious foreshadowing, to a a thriller dénouement that involves a bunch of dimension-hopping assassins equipped with diminutive lightsabres. Brasyl's worth a look: whenever McDonald's imagination slips free of its narrative constraints it leaves many of his contemporaries standing. Those in search of the full experience, however, might check out the back catalogue first.

Orion £18.99