The SFBC introduced me to lots of great authors when I was in high school. I tended to buy the omnibus editions, because four or five books for the price of one! (Yeah, I don't think anybody was surprised that I ended up with a degree in Economics.) But what omnibuses! Asimov's Robots and Foundation series, Asprin's Myth Adventures and the Sanctuary books, Zelazny's Amber, Lieber's Fafhrd and the Gray Mouser, and that's just off the top of my head. Some of those I've had to replace, because I read them until they fell apart. (The flip side to cheap Book Club editions is that they're cheap Book Club editions. :) )