Between the apes and the angels stands Bernstein's copy desk, bastion of custom, common sense and the triumphant double genitive. He's the author of The Careful Writer and Watch Your Language, a former Assistant Managing Editor of The New York Times, and if you write you are probably already in his debt. Here he takes a sensible item-by-item stand on some of our language's sorer points (the split infinitive, for one), demonstrating the difference between verbal leniency and outright laxness. And what a relief it is to find that you don't have to put your better foot forward, that you can graduate from college, celebrate a birthday every year, eat healthy food, go slow (people have been doing it since 1500) and stick up for your friends (though not in print). It's clear from Bernstein's clever commentaries that the experts don't have all of the answers -- and the final authority even for him is ""respectable writing,"" whatever that is. He seems to know, so trust him. Sections on words, syntax, idioms and style are appended with three classic blacklists, including Bierce's notoriously arbitrary Write It Right.