Safire's war against bad grammar; On Language, by William Safire. New York: Times Books. $12.95.

In our age of political and corporate double talk, cliches, euphemisms, and other crimes against the English language, it is heartening to know there is someone unwilling to let them off without a sentence. William Safire objects to wood burning stoves being called "energy systems," and airline stewardesses who say "now at this time." These objections, contained in this collection of columns from the New York Times Magazine, make witty and insightful commentary on the fate of language in a society geared toward telephones and computers.

One of Mr. Safire's pet peeves (the biggest one being the term "pet peeve") is what he calls the "prettifiers," a group of sugarcoated words dear to the hearts of advertising copywriters. In one of his most amusing essays he takes to task some of the worst -- used cars that are "pre-owned" and bumpers called "impact attenuators." Another dislike is receiving correspondence on stationery imprinted with "From the desk of . . . ." He proposes a suitable reply, "Tell your desk, which has written to me recently in your name, that it should clean itself out and stop trying to pass itself off as a source of correspondence."

But what really comes under attack in this collection is fuzzy thinking that causes people to substitute worn-out phrases for communication. According to Mr. Safire, one of the most abused is the ubiquitous "Have a nice day," phrase automatically used at a conversation's end whether appropriate or not. As proof he cites an episode that took place recently in a courtroom where a judge sentenced a man to a minimum of seven years in prison. The judge's parting words to him were, "Have a nice day."

Perhaps the best aspect of journalist Safire's comments on language is that they are not stuffy or even immune from mistakes themselves. While he is busy listening and watching for the abuses of language, his readers are quick to spot the misspellings and misuses (misusages?) that occasionally crop up in his columns. Almost half the book consists of letters the columnist has received, some catching his mistakes, many more offering nuggets of lexical information. Although what Safire has discovered about word origins and their current usage made good reading, the inclusion of what his readers have to add makes them even more so. A good accompaniment, also, are the very funny little illustrations by Kimble Mead.

Whether or not one has encountered these essays in their previous form, they make both entertaining and thought-provoking reading. By casting an uncompromising eye on the way we use our language, the author succeeds in telling us a lot about ourselves.