There is a lot of websites about checkers (draughts), e.g. Jim Loy's page is a good start. I like Bob Newell's page very much. Books in English (about checkers) are also no problem, but I personally don't know any book/website in English about the Czech variant, there are AFAIK only some about the "pool checkers" (see Amazon). It's a pain to get some books even in Czech... :-)