Like any collection of essays republished from other sources, this one--the third of many such anthologies from Gould--is a mixed bag. All but three pieces originally appeared in "Natural History" magazine, but Gould updated many of them with postscripts incorporating responses to and criticism of the original articles.
The range, as always, is impressive: tours of the controversies and unforgettable characters that pepper the history of science; examinations of the politics of science (which, sadly, hasn't changed much in 25 years) and the threats to teaching posed by creationists; explorations in paleontology and evolutionary theory; and some dabblings in "hard science" that might leave a few folks scratching their heads. There's even a typical Gould curio reminiscent of his essays on baseball: an analysis of the inexorable trend towards smaller Hershey bars. The only truly outdated essays are those which focus on genetics and the discovery of the structure of DNA.
For me, the defining moment in this collection is the question posed by Gould: "Is a zebra a white animal with black stripes or a black animal with white stripes?" It's really a damn good question, but to be honest, such a problem would never have crossed my mind. (I feel doltish for not even knowing that there are three species of zebra.) Gould's certainly not the first biologist to consider the issue, but he's surely the first to offer for the everyday reader not one, but three easily understood and (one might even say) riveting essays on "striped horses." And that's just what makes Gould's works so worthwhile: a charming combination of his fascination with history, his inquisitiveness about nature (especially in areas "outside his expertise"), and the patience needed to write clearly about such matters for the non-scientist.