It's a miracle: look up books from home
(joking!) See linked tip of the week from NY Times - I guess they didn't know that most libraries have had their catalogs online (with real time availability info) for more than 10 years?
Oh, but still, I am happy they've pointed out WorldCat and it is useful if you have access to multiple systems as I do (within about a 20 minute drive from my house: 2 community colleges, 3 university libraries, 3 county public library systems, oh, and my research lab library)