Opera buffs, beware; The Illustrated Encyclopedia of Recorded Opera, by Peter Gammond. New York: Harmony Books. $17.95.

Normally there would be no reason to discuss an inferior book of this sort, but in the case of "The Illustrated Encyclopedia of Recorded Opera," avid fans and curious neophytes alike will undoubtedly be tempted to spend a considerable sum on a book that's utterly deficient.

The lavishly illustrated volume, originally published in Britain, is billed as a comprehensive guide to operas and recordings. It includes lists of recommended records, as well as a section devoted to the 100 most important singers of the of the recording era, but the names seem to have been chosen on chauvinistic rather than artistic grounds.

Most of the book is devoted to the mentioning of some 550 operas. If the sleeve not did not call it indispensible for anyone interested in opera, if the color reproductions were not so handsome, if the idea were not so good, then perhaps the book could be merely ignored. But Mr. Gammond hasn't done his homework, doesn't really know the recordings, and doesn't seem to understand what makes opera tick. Don't be misled.