Think what you want, but my opinion is that studying at a library(rather than studying at home) is for tools who want to convince themselves that they're getting work done. You won't really get any more done than you would have at home, I don't care what you think it just doesn't happen like that unless your house is some kind of warzone.
The only real excuse that I can think of for going is to use books that are available at the library, but not at home. eg. student answer books, study guides and so on. If you really MUST go to a library, avoid going with friends because you'll get distracted or at least sit on your own in one of the cubicles.