More specifically, why are her books so damn popular?
I read My Horizontal Life, and it sucked. It wasn't very funny, and it wasn't at all titillating. If an author writes such a boring memoir about sexual encounters, I can't imagine her other books being worth reading. The message I took away from My Horizontal Life is that Handler is just as shallow and dumb as all the one-night stand guys she makes fun of.
As a friend put it, "Do you realize this woman has built an entire career on being a drunk and a slut?"