Hmm. True crime isn't often known for being well written. But check out Public Enemies by Bryan Burroughs, <em>Columbine</em> by Dave Cullen, <em>The Devil in the White City</em> by Erik Larson, and of course, <em>In Cold Blood</em> by Truman Capote. T.J. English has written some supposedly good stuff, and (being from Boston) I can recommend some good books on Whitey Bulger, including <em>Brutal</em>, <em>Black Mass</em> and <em>Rat Bastards</em>.
If you're looking for stuff on actual murderers, it's going to be a little harder. Most of that stuff is crap. I guess the old standbys are <em>Helter Skelter</em>, <em>The Stranger Beside Me</em>, and <em>BTK</em>.