I've got a stack of books that I'm making my way through at the moment - and the top of my list is The Beltway Bible.
I've worked on the Hill and having also worked in politics in the UK, I'm a total geek for books which spell out everything you need to know about our political institutions. Written by political reporter and editor of Huff Post's Washington DC Bureau, Eliot Nelson provides a satirical and absolutely fabulous look at the A-Z of everything you would want to know about the Hill.
From why everyone in Washington is an 'expert' to the value of certain Twitter accounts, this is definitely a book for the political fanatic in your life. Nelson thinks that this book will only be read in the bathroom - something I have to disagree with! This is one I'll be dipping in and out of over the years of political ups and downs that are to come.