<B>Petra Connor's back</B>Hot on the heels of his October collaboration with wife Faye (<I>Double Homicide</I>), Jonathan Kellerman is back with a new Petra Connor novel, <B>Twisted</B>. Fans of Kellerman's work will remember Connor from 1999's <I>Billy Straight</I> and last year's <I>A Cold Heart</I>. In <B>Twisted</B>, Connor has been given the unenviable task of baby-sitting a genius, a college-age Hispanic kid with a penchant for statistics. Isaac Gomez plays on his computer, endlessly crunching numbers in an attempt to show that crime solving need not necessarily be hands-on. Although perhaps a bit far-fetched, Isaac's theories bear looking into, and Connor agrees to consider the data along with other evidence in a number of cold murder cases. When the clues begin to coalesce, Connor realizes that a) a dangerous serial killer is at large and known only to her, and b) another killing is imminent. There is little time to lay a trap, and so many opportunities for something to go wrong, not the least of which is the illegal handgun that Isaac secretly carries in his briefcase. Jonathan Kellerman is at the top of his game these days; his novels are briskly paced, shrewdly plotted and staffed with credible and sympathetic characters (except of course for the bad guys, who are deliciously flawed and evil).