The author spends two years in the pickup artist community and learns pretty much everything there is to learn about seducing women - shallowly, that is, a fixed routine to get women to give him their numbers and/or sleep with them, as well as transforms him from a generic writer nerd that doesn't get any to Mr. Popular, both in clubs and in the online pickup artist community.
By the end of the book, after things have gone ridiculous with the top pickup artists all living together in a big house in Hollywood together with, of all people, Courtney Love, and things are all falling apart, the author realizes that it's pretty much all bullshit. The ability to pick up pretty much any woman you want makes one shallow and hollow; it's a way to fill up a gap inside, but only permanently. This is mostly obvious in the main pickup artist the author follows, Mystery, who has multiple emotional breakdowns and drops back into depression in the book; a fucked up childhood made him into what he is, and his rational thinking and things were unable to truly fix it, especially after he loses women he really cares about (but neglects, 'cause that's how he works).
tl;dr. By the end of the book, the author meets the guitarist (or something) of Courtney Love's band, who he takes a liking to. Problem is, she's impervious to the whole set of pick up artist techniques. Eventually, turns out she does like him, but only if he's himself and loses all the pickup artist bullshit techinques.
So again the basic concept is regurgitated: Just remain yourself. (cleverly omitting the fact that if the author didn't go on his quest and slept with hundreds of women in that two year period he would never have ended up the ridiculous situation he was in and met that woman, but w/e).
I remain unconvinced of that, but eh
. Good read, go get it for the lulz.