The Science of Discworld III: Darwin's Watch by Terry Pratchett, Ian Stewart and Jack Cohen ISBN 0091898234
This book is the third in a Discworld sub-series that examines and explains science through the eyes of the wizards of Unseen University. This particular volume follows the wizards after they discover that somebody has changed the history of roundworld (Earth to us natives) so that Sir Charles Darwin didn't write The Origin of Species, thus setting back the development of science and technology by approximately 100 years or so. Unfortunately this meant that when the big freeze featured in the end of the last book comes along the humans are still stuck on Earth with no space elevator(s). Bugger.
In between the wizards adventures, as they try to figure out who messed up the history they preferred and how to undo (redo) it all, we investigate the arguments both for and against Intelligent Design, the various theories of time-travel (and why some of them are more or less well thought of), as well as the nature of infinity (the number as well as the spatial concept).
I found the Intelligent Design debate section very well written, with the various scientific arguments used by both sides clearly laid out, and the ID proponents weak science rather effectively illuminated. That is not to say it answers the question of ID vs. Evolution in a way to settle the debate, rather it shows why the current examples used by the ID crowd are such bad examples and they should really find better ones (if they can).
The time travel, infinity and cosmopology sections had some very heavy philosophy in parts, which I soldiered through for some perverse reason, but if it isn't for you I would suggest you could skim those chapters and still enjoy a good read.
One neat piece of information I picked up was how John Gould (and hence the WA Museum) managed to acquire Darwin's entire collection of Galapagos island finches. It seems that upon returning to England after his historic voyage Darwin simply gave them to the Zoological Society, not thinking them worthy of much interest. The societies orthnithological expert was noted naturalist John Gould. It was Gould who made the amazing discovery that all of these birds were in fact descended from the one species, even though they looked remarkably different to one another, so that years later Darwin used it as an example in his famous book.
I rate this book 9 out of 10, as the first section is very interesting and relevant as the whole ID vs. Evolution debate goes on in the US, 100 years after the question was well and truly settled in Europe (and Australia). The fiction parts illuminate nicely the points the authors are trying to make while still being very entertaining.