Interesting, even if you aren't a book lover. Take a guided tour. They go often and are free. You'll learn a lot about the building, collection, etc. The building is very impressive. I really liked seeing Thomas Jefferson's book collection and the progress they have made in replacing the books that were lost/damaged due to a fire. It is only a few blocks from a metro station, so it is easier to get to than some of the Smithsonian buildings. Admission is free. Word of advice- your bags are searched on the way out, so this is not the place to go if you have just come from a book store, etc.

The Library of Congress almost made me cry. I am a huge bibliophile and just walking into that main reading room was overwhelming. Knowing I could have almost any manuscript pulled for me and then spend hours sitting in the reading room enjoying it was amazing. The building itself is a masterpeice. It is huge and beautiful and has amazing architectural details. I took probably a hundred pictures while I was there.

Totally worth a visit. Take a guided tour, but be careful they are only offered like 3 times a day. If you are really interested with a US ID or an international passport you can go down and get your reader's card so you can actually go in the room and explore the books. I think its worth it!

The most beautiful building in Washington D.C.. Taking one of its free public tours is a must. Whether you care about all of the books or records or not, the building is gorgeous!

If you're a book lover as I am, this is Heaven!! (the Gutenberg's Bible is exhibited there). And the art and architecture are quite amazing too.