While you might expect Dawkins' classic to be terrifically interesting (and you'd be right), you'd probably expect it to be a bit of a slog. In this respect you'd be completely mistaken - it flows beautifully, and is seriously difficult to put down. And the whole way through you have the wonderful sense that you're being educated as well as entertained.
The book starts right from first principles, describing a plausible theory for the origin of life, and explaining how more and more complex molecules could have formed in the 'primaeval soup'. Eventually a molecule arose that could replicate itself, and life has never looked back. Dawkins goes on to define a gene, which turns out to be quite an important step (I thought I knew what the word meant already, but I was wrong), and relates how genes have indirect control over what he calls 'gene machines', i.e. living things. Subsequent chapters then detail various survival strategies, 'altruism' and how it can be explained genetically, tensions between sexes and generations, and a new replicator, the 'meme'.
One of the most fascinating aspects of the book is the way that Dawkins draws on game theory to assess mathematically the most sensible way for a gene machine to act. In particular, the sections on 'the Prisoner's Dilemma' (a specific game theory scenario which crops up all over the place in nature) are, to me at least, a radical new way of thinking of many problems in (human) life, and how we should approach them. It could have ramifications for politics, social policy, economics, and the environment, to name only a few. Like all the difficult concepts in this book, Dawkins explains this simply and thoroughly, and the reader never feels patronised. And if you ever feel a bit stuck, a captivating, and often extremely bizarre, illustration is selected from the animal kingdom to clarify the point. Dawkins is also refreshingly willing to state that certain aspects of this theory are +the truth+, a brave claim in our muddled, PC society.
I would therefore thoroughly recommend this book to the general reader. It's stuffed with hugely stimulating concepts (Dawkins' own 'meme', or replicating idea, is a paricularly rich one), and wonderful snapshots of the animal kingdom. Be warned though, it may take over your life for a while - personally I feel tempted to jack everything in and go and take a bilogy degree!