I read this while sitting in Powell's one day, skipping most of the "Girl" sections (though I'm a girl myself) and reading the horny boy sections with great enthusiasm. While the book has good sex scenes and is funny, it's all gimmick and no action, and that only goes so far.

Yeah, the gimmick definitely takes precedence over the action.
McLaughlin obviously had more fun with the boy sections, because they're way less boring than the girl ones, yet much, much sillier. That's probably because Jack's only two emotions are angry and horny. Which is fun to a point...