Other mysteries may deliver more intricate plots, more assiduously researched atmosphere, or grimmer glimpses into the darker realms of the criminal mind, but none quite matches the one quality that Sue Grafton's detective novels have in spades: voice. ''J'' Is for Judgment, the 10th in an alphabetically ordered set of mysteries that began with ''A'' Is for Alibi (1982), further immerses fans of the series in the best first-person-singular (actually, first-person-twice-divorced) storytelling in detective novels: investigator Kinsey Millhone's wry, depressed, my-life-is-hell-but-I-like-it-that-way narration. Even when she isn't doing much in the way of investigating, Millhone's observations make for a very easy ride. Imagine a younger, female Jim Rockford, and you have an idea of the unfussy assurance with which Millhone and Grafton tell a story.
Good thing, too, that the narration is so solid, because what ''J'' offers in the way of mystery is awfully low-key (at least until its very shrewd, Body Heated ending). As Millhone looks into a ''pseudocide'' the possible reappearance of a con artist who may have faked his own suicide years earlier the point is less the plot than the way the detective is spurred to examine her own murky past. (As Millhone followers know, her parents were killed in a car accident when she was 5, and personal information in the first nine books has been offered with the wary parsimony of someone who isn't quite sure she can trust her readers yet.)
Millhone's revelations about her parents and grandparents offer a real reward for readers who have stuck with the series so far, and they lay the groundwork for volume ''K'' to go in several compelling directions. But as the Millhone novels approach their halfway point (''M'' Is for Murder? Malice? Mayhem?), Grafton has one problem to solve: Her heroine, now 34, has aged only two years since she first appeared in 1982, which means that she's still stuck investigating insurance fraud in the mid-'80s. For the thoroughly modern Millhone, the most contemporary of sleuths, being trapped between Reagan administrations seems the unfairest of fates. Here's hoping Grafton doesn't let her become a period piece. B+