Yah, don't be a scrote - do your homework.
Think about breaking the problem down. You'll want to do this object oriented. Start thinking about a 'book' class.
It will have attributes such as Title, Author, ISBN, Purchase Date etc
It will have functions such as 'bookOut' and 'bookIn' which will model behavior of the object (i.e. when people borrow it and return it)
Then think about a 'Customer' class, which will have stuff like Name, Phone Number, Address etc
Once you start modelling the components you need (i.e. information you need to store) you'll need to think about the behavior of these objects (i.e. a book can be AVAILABLE, ON LOAN, MISSING etc, a customer can be ACTIVE, OVER LIMIT etc). You can start designing your system on a piece of paper, by creating an object oriented design, as well as a database schema.