"The Cambridge Encyclopedia of the English Language," by David Crystal. Cambridge University Press. 480 pages, with illustrations, diagrams, maps and tables. $49.95 An irresistible browsing joy for anyone with even remote interest in the use and abuse of the language. Not a substitute for anything I have ever seen, now that it is in hand, I can't imagine being without it. It's full of wondrous things from the history of the Doublespeak campaign to the origins and evolution of the language. There are splendidly polished sections on grammar, punctuation, sentence structure, everything you would expect and a great deal you would not. Only one reservation: Once you have it, you may disappear from sight for days or weeks on end.