He covers a lot of the ground that he covers in later, longer books. His explanation of mitochondrial Eve is the best that I have found, even though it may be dated (15 years old)
"How did the replication bomb we call 'life' begin and where in the world, or rather, in the universe, is it heading? Writing with characteristic wit and an ability to clarify complex phenomena, Dawkins confronts this ancient mystery."
- From back cover
River Out of Eden is a short book describing, essentially, the motivation of DNA to survive, and what that means about life and humanity. It's also got a few probably oft-repeated rational arguments used to deflect the non-argument "But it can't be!" complaints that have been leveled at evolution over the years.
It's a quick, reasonably light read (unless you argue with the premise, probably). I enjoyed it.
Excellent! Richard Dawkins is able to write about the very difficult and complicated subject of evolutionary biology in a way that makes it accessible without dumbing the material down. A very interesting read. I gave it 5 stars.