Is there anything better — or rarer — than a clean, adequately illuminated used book store? Patten Books is tucked in an unassuming strip mall between the vast used-car dealership lots of Kirkwood and Glendale, but don't let the nondescript storefront fool you. Owners Keith and Nancy Patten run an extremely tight ship. Shelves are massive and well dusted, there's nothing on the floor except for conveniently placed step stools, and the books — oh, the books. The vast bulk of them appear to have been read by a little old English professor from St. Louis Hills who never exceeded 50 words per minute. Spines are tight, covers are intact except in the case of something so rare that a little battering around the edges is to be expected, and the stench of mildew is nowhere to be found. The selection is similarly aces. You'll find no multitudes of airport bookshop bestsellers or heaving piles of moist-paged romance novels. Mr. Patten's a discriminating buyer, looking for the excellent and the unusual. The poetry section features reedy volumes of Ted Hughes, Donald Finkel and Mona Van Duyn; such pulpy authors as Clark Ashton Smith rub shoulders with cerebral brothers Arkady and Boris Strugatsky in the sci-fi/fantasy department; and every individual soldier's experience from both the Civil War and World War II is apparently documented in the history section. Prices are generally half the cover price or less, with the notable exceptions of the rarities kept behind the cash register.