A collection of surprisingly layman-friendly articles on evolution. The articles try to explain why some animals have apparently unique structures and how they came into being. The explanations are almost Lamarckian but with periods of accelerated development where random changes unexpectedly help an organism survive.
There are also explanations on how specific complex traits have arisen - essentially refuting some peoples commonly cited examples supporting an anti-evolutionary stance. The book has aged well, unlike some other scientific essays. A good read for anyone interested in evolution.