This book is an exceptional history of science because it was written by a very prominent scientist. It's hard to imagine that a better history of biology will become available anytime soon. Especially the chapters on diversity and evolution are fascinating and understandable even for a layman, the final chapter on inheritance is more difficult because some familiarity with cell biology is required. At the end there's an interesting synopsis of some philosophical consequences drawn from the preceding chapters. If you're interested in the history of biology, this is the book you should begin with.