I personally hate this one. I had a big time getting this out...
For Edward, the library was like another home.
There, surrounded by hundreds of books, Ed had chance to relax and think something else than work and responsibilities, to do something he really enjoyed.
Books were like friend to Ed. They didn't question him, didn't judge him or avoid him because of those stupid mistakes he had done. With books Ed lived with perfect concert.
In library Ed really felt like home. The other place like that was with Roy Mustang.