Suggest you look here for some concepts on library databases. There is a whole section for libraries.
Regret to say that your posts indicates you need some background information on database normalization since you are mixing book information with transactions and users.
There is a nav pane here that covers this and many other design concepts http://www.fmsinc.com/free/newtips/primarykey.asp
A bit of homework will save you a lot of aggravation later on.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.