A good collection of science fiction mysteries, along with an explanation of that relatively obscure sub-genre from Isaac Asimov. I've read a fair number of SF mysteries, and had read most of the ones in the book; most of them are excellent examples of the form. The leading story, "The Detweiler Boy" by Tom Reamy, was not particularly good; putting a relatively weak story first in an anthology is an unfortunate flaw.

But there are a number of gems here, including Larry Niven's "Arm". "War Games" by Philip K. Dick, was simply not readable for me; I can take some PKD, but only in mild doses - and not a lot of it. I don't know if it was the mood I was in, or if the story was particularly Dick-ish (sorry, couldn't resist), but after a page or two I simply skipped that story altogether.

That said, the vast majority of the book is excellent and well worth reading.