I really enjoyed this book, and it's a real pleasure to be able to write a positive review about it. Many fantasy/science fiction novels have alternate worlds or universes, and quite often they come across as very similar - this one is very different, as it's a computer-generated world populated by some of history's worst tyrants, which was intended to be used to train armies for extreme warfare.
I found it fascinating, and very funny (surprisingly enough) at times. It comes across as the deadly lovechild of David Cronenberg and Douglas Adams (if only that was possible!); it was refreshing to find myself chuckling away because a lot of these type of books are so humourless right the way through - it's written with a real verve and the author obviousy enjoyed himself when he wrote this. Also, the historical characters are very convincing - quite chilling portraits at times.
The icing on the cake is the pacing - the story gets going right away; one of the problems I have when thinking about reading books that look like this one is that they always seem to take at least 100 pages before the 'other' world is involved - not here, thankfully. As the story builds, the chapters end with some real cliff-hangers that make you keep on going even when it really is time to turn the light out.
One caveat - swearwords are used, and there are the occasional mildly explicit moments. This is a book for adults - although I'd consider it for mature 15-year-olds and above perhaps.
I'll spare you the plot details, as they're already covered by the other exemplary reviews here - you'll know by now whether this is the sort of book you'll want to read. A fair proportion of the book deals with a battle, but this is a book which should appeal to both male and female readers. I could write a HUGE review on this wonderful book, but the best thing I can say for it is that I wish I'd written it, and I'm going to go out and get a signed first edition when my finances recover from Christmas.
Very highly recommended - I can't imagine lovers of SF or fantasy not loving it.