TAKEDOWN: THE PURSUIT AND CAPTURE OF KEVIN MITNICK, AMERICA'S MOST WANTED COMPUTER OUTLAW -- BY THE MAN WHO DID IT Tsutomu Shimomura, with John Markoff (Hyperion, $5.99, first published in 1996) Who is Kevin Mitnick? Once the world's most-wanted cybercriminal, he nabbed information from unsuspecting phone-company employees and the like, which gave him insider access to computer networks all over the world. The hyped ''takedown'' isn't particularly lively (tracing cell-phone calls, that kind of thing), but this is a well-sourced, if not particularly sprightly version of a pasty-faced social misfit's story. B