like matters, and then a speculative chapter regarding future languages, essentially a didactic piece on language change with application to science fictional treatments of time-travel. It leads into a discussion of nonscientific claims about the "fourth dimension" in general. This part of the book also includes reviews of Immanuel Velikovsky's Worlds in Collision and Erich von Däniken's Chariots of the Gods?, both of which de Camp discounts. Reception Critical reviews of the book were generally positive. Writing in the wake of its release, Tom Easton observed in Analog Science Fiction/Science Fact that "[i]f you know L. Sprague de Camp's work at all, you know what to expect ... He's always readable and entertaining, as he sticks his thumbs into gaping holes of fact and logic ... He's full of the straight dope (though he often doesn't go into things as deeply as I would like)." He urged readers to "buy the book." Michael Schuyler, writing for Library Journal, took a more neutral stance, judging only that "[m]ost of these mysteries have been well documented elsewhere, and De Camp [sic] presents no revelations." The book was also reviewed by Darrell Schweitzer in Science Fiction Review v. 10, issue 1 (Spring, 1981), p. 22. More recently, an exhaustive review from 2007 sums up the book as "a very pleasant and readable collection of essays, an excellent and classical example of skeptical writing and debunkery of various kinds of pseudoscientific and paranormal nonsense." The reviewer notes de Camp's "accessible, down-to-earth style," humor, and story-telling expertise, as well as "somewhat conservative opinions ... which occasionally show in his writing." Its conclusion is "[o]verall I highly recommend this book." Notes 1980 non-fiction books Science books Essay collections Books by L. Sprague de Camp