It only becomes a problem - when you collect more books than you actually read. Occasionally, I have to institute a "no new books" policy, until I finish reading what I have on hand. In Americorps, this policy pushed me through Grapes of Wrath, East of Eden, Native Son and a handful of other short novels. Well, now I'm 15 deep - and I'm bringing back my book prohibition.
I'm hating myself for buying Atlas Shrugged right now... Looks like it's gonna be a long, long... long time before I'm allowed in a bookstore again.