I can only recommend The Girl Next Door from the options being polled because it's the only one I've read. I had to put the book down for a few months and then come back to it—and I quit before much of the physical abuse started. I finished Girl in an afternoon once I'd hardened myself enough. It's stuff tough. There are certainly some problems, some of them stemming from Girl's being told from a first person perspective (or at least from its being told from David's point of view), but the only things that have elicited a similar emotional response from me have been other Ketchum works. Avoid the film, though; it's not nearly as powerful.
Ketchum's short story collection Peaceable Kingdom is terrific. Give it a shot if you haven't already after you've read a novel.
Ketchum is one of the best writers alive as far as I'm concerned. He's got an engrossing pseudo-minimalist touch that's to be envied. [That's a pretentious way of saying that each of his works is all killer and no filler and that his prose will dig into your skin like fishhooks and not let go.]
I've only read Offspring and The Girl Next Door. And, really, it's a tough call on which one to read first. Maybe go with The Girl Next Door. If you can make it through that book, you can make it through any of his books, I guess. And besides, I'm sure you could learn some things from how The Girl Next Door was written.
For example, I started with Fear and Loathing in Las Vegas, rather than Hell's Angels. And with Cormac McCarthy, I read The Road first. I dunno. I guess it's my way of getting introduced to new authors in the "best" manner possible. For example, I loved The Rum Diary. Had I read it first that probably wouldn't be the case.
Whoa. My exceptions exactly. But since then I've followed the chronological method.
Also for the class mates of the Ketchum class, you can go in there now. I started an introduction thread so we can get the boards busy with conversation.
If you haven't already read it, read Off Season before Offspring. Offspring is the sequel to that book. The Woman is the sequel to Offspring if you want to read them as a trilogy.
EDIT: I didn't notice the last post here was in 2012, but that's still my 2 cents if anyone cares.