Sometimes it's hard to describe a book, or even to work out exactly why you liked it. But after a spell of the wide-screen baroque of radical hard SF space opera, it was time to read something a little more introspective. The "to-be-read" bookcase is a study in book-buying archaelogy. There are little bits of series, waiting for the rest to be found before I read them. Then there's the detrius of countless trips to Hay on Wye, or misguided purchases on con tables when that magic "5 books for £10" sign appears on the last day that I can never realy summon the enthusiasim to read.

And finally there are those good-intentioned purchases. Usually they are "I really must get round to reading the entire Clarke Award shortlist" type events, and Alison Sinclair's Cavalcade, part of the 1999 short list, has been sat around for quite a while, before finally drifting to the top the pile just as I finished Permanence.

It's the day after tomorrow, and aliens have arrived. Or at least their ships have, bringing a simple, and intriguing message: if you want to come along with us, fulfil these simple conditions at this time. The story opens just after that moment, when the gathered crowds suddenly find themsleves in a set of gently glowing caverns. Electronic equipment isn't working, and two hours seem to be missing. If this is the ship, where are the aliens, and why is no one communicating with them?

Constructed as a series of interlocking narratives, Cavalcade follows the travails of a group of random individuals (colonists? visitors? guests? abductees? recruits?) as they struggle to build a society, and at the same time discover the truth behind their mysterious surroundings. There's conflict between the military, the scientists, and the increasingly fragmented communities - and a clock that's quietly ticking away in the background, one that they can't quite perceive. A misfit killer and a pregnant runaway are the keys to solving the mystery, but they may not actually want to be part of the solution.

Sinclair's characters are well-drawn, and she's obviously very much in love with a couple of them, as they stand out head and shoulders above the rest of the undistinguished crowd. A working scientist herself, it's not surprising that there's a focus on the process of understanding, of careful hypothesis and the application of the scientific method to the problems, and the resulting solution is intriguing and, to a certain extent, unexpected. The world is well drawn, and there's an element of claustrophobia in the caverns of the ship's heart that captures the uncertainties and the fears of their new inhabitants.

Still, despite its likeable qualities this isn't a wonderful book. It's a light read, with some deeper elements, but it doesn't drive the genre forward. If anything it looks back to the past, and the early novels of Octavia Butler or Kate Wilhelm. In fact, I find it difficult to see how it reached the short list, as all-in-all, this feels like a minor work by a promising young author. Maybe, 5 or 6 novels down the line, we'll see something earth shaking, but this most certainly isn't it.

So, just three more books to read before I finish the 1999 short list...