First, tell me what genre do you prefer? And book must be easy or difficult?)

if you prefer .fb2 format (fiction book), then visit http://fb2lib.net.ru. there are many works in English as well.

Еще сайт http://lib.ru/

http://tululu.ru/article_online/ http://allbooks.in.ua/

http://lib.rus.ec/book http://lib.rus.ec/a/18736