I just (finally) finished reading Richard Dawkins' The Greatest Show on Earth. Normally, I would write a bit of a book review, but I am kind of swamped right now with trying to finish my graduate career and move on to a post-doctoral fellowship that is waiting in the wings. I will say that the book was excellent and very well written. I am always amazed at Dawkins' ability to distill important concepts in biology and evolution and convey them so simply and elegantly. If you want a book that gives you numerous readily understandable explanations of the evidence for evolution (and instances of UNintelligent "design") it is certainly a must read.
And though it took me a while to finish, I imagine someone not writing a dissertation would be able to read it cover to cover in a week or less (I know some who took it all in in one sitting.)
All said, a great book, I highly recommend it, and, if time permits, I will post a more thorough review of the book in the near future.