I really hope you mean borrow. I've never had to pay to take books out of a library.

I much prefer to buy. My wife and I are building a home library. When she moved in with me after the wedding she brought 15 bankers boxes of books with her. Even if we buy a book and don't like it somebody else probably will, so onto the shelf it goes.

There is no such thing as a fireproof bag. You can get fire-resistant bags and safes, but even the best consumer model safes will buy you two hours tops in a normal house fire.