The Algebraist by Iain M . Banks
A far flung solar system has been cut of from the rest of the galaxy due to its only wormhole (allowing instantaneous travel) being destroyed. Warned that an invading fleet will be arriving at sub-light speeds in a few years, the system's ruler conscripts a intelligent but moody loner with secrets of his own into a desperate mission to locate a probably fictional list of alternate wormholes from the capricious alien race that lives in the system's gas giant planet. Along the way loyalties are tested, nothing is quite what it seems, and ripples from events from the distant past collide to throw the protagonist in unexpected directions.
Unlike all of the other Iain M. Banks books I have read, this one is not set in the culture universe, but an entirely new setting where culture-esque AI Minds have been wiped out (or have they...). The bulk of the book is spent inside the society of The Dwellers, a gas-giant living alien race who possibly hold the key to a hitherto unknown system of wormholes.
This was an excellent airport read, long but never dull, with plenty of finely detailed descriptions of the alien worlds visited. Whenever the main protagonist's quest is getting bogged down, the action shifts elsewhere - usually to a massive space battle for a quick change of pace. It is my opinion that this technique should be more widely used in literature; imagine how much better Wuthering Heights (for instance) would be if an floating armada suddenly appeared in the skies above the moors. Chuck in a few ninjas and you have the makings of an absolute classic.
If you have read any other Iain M. Banks books you will know what to expect, despite the new setting it is quite like the his other books featuring a intelligent but moody loner with secrets of his own forced into a far-ranging quest in which loyalties are tested, nothing is quite what it seems, and ripples from events in the distant past collide, etc, etc. The Algebraist lives up the high standards set by its predecessors, but does not exceed them.
My one criticism is that the solution to the central mystery is fairly easy to guess if you have been paying attention, and it should have been obvious to many of the main characters right from the start. But apart from that quibble, The Algebraist was an enjoyable read.
Recommended if you like this sort of thing.