Is there any website where I could get a sign language book for free?
There are some websites that you can sign up to get free sign language books. One site that you could visit is the Gallaudet university official website. Go the site by clicking the following link for more information http://www.gallaudet.edu/clerc_center/information_and_resources/info_to_go/language_and_literacy/asl/learning_asl.html.
http://www.onread.com/books/key-sign-languageuse in-browser viewing, dont download