Jisho

I think they just translated it as books, plural, because it's almost exclusively used as a part of 図書館 (library) or as an abbreviation for library time at school or something.

The monolingual definition for 図書 is 書籍。書物。本。ずしょ。

So, there's no implication of it being plural by default or anything.

But yeah, basically... don't use it to refer to a book or books in everyday conversation. People will find it odd if use something other than 本 for the most part.