There are many chess encyclopedias. Most, however, suffer from three faults, to a greater or lesser degree: (1) many omissions (especially of problemists' terms); (2) inexact definitions of chess terms; (3) dishing out old, stale fables -- indeed, libels (such as the claims that Morphy had a fetish for women's shoes, that alekhine was a "sadist", etc.) -- as if they were fact.
All these faults are corrected here, in the Ocford Companion to Chess (OCTC). The authors are very careful to include practically all chess terms, and are especially careful to include all important problemists' terms (excluding, so far as I can tell, only names of themes that are nothing more than a slight variations on a basic idea -- the basic theme itself always has an entry). The definitions are exact; for example, "resignation" is not lazily defined as "giving up a lost game": it is noted that occassionally, "masters resign in drawn, or won, positions". Above all, the biographies of vitually all important players (up to the time of publication -- you won't find an entry for Magnus Carlsen...) are treated factually and with respect, avoiding both unfounded smearing of the chess world's designated "villans" (Alekhine, Staunton) or hero worship of its "heroes" (Morphy, Capablanca).
This is not to say that the book is "revisionst" for revisionism's sake, trying to make villans into heros and vice versa. It does not, for example, belittle Capablanca's chess genius or ignores Alekhine's cooperation with the Nazis. But in fairness to Alekhine, the companion -- after outlining the details of Alekhine's cooperation with the Nazis -- also notes that, such issues aside, Alekhine played in 44 strong tournaments since gaining his master's title, winning or sharing first in 25 of them. In fairness to Capablanca, the companion, after taking note of the long period when "he was considered practically invincible", adds that he failed in two tournaments when returning to chess after a three-year hiatus.
So much for avoiding faults found in other books. But that is not all. The OCTC has many independent merits. Above all, it is a treasure trove of reliable information about the game of chess in general, and of its lesser-known cousins (chess variants, problemists, postal chess, endgame studies, fairy chess...) in particuar. Even seasoned chess enthusiasts are bound to find much in this book they have not heard of before. For example, few people -- to pick a few entries at random -- know how the camel (a fairy piece) moves, what the Dombrovskis theme is, or any biographical details about Pirc (apart from him being the inventor of the Pirc defense: quick, what was his first name?).
If you don't know the answer to all, or any, of these, you will like this book. There is a lot in there for all who are interested in chess.