Where is the Libaray of Congress and is the President's secret book real?

The library of Congress is located in Washington DC. It holds all the books published in America. You've most likely heard of the President's secret book in the popular movie National Treasure. I'm not exactly sure if the book is real, for I've never even been to Washington DC. I wish to believe its real, cause that would be really cool! But you'd have to ask a president if its real, because if its so secret, nobody else would know besides a president, hopefully. It's a secret right? Its a conspiracy theory, do some research, and maybe you'll answer your own question! Some people say its real, some people don't, its a yes or no question but its much more complicated. Hopefully that answered your question.