I'm all about combining different uses in one room but I've never seen a combination library/bathroom. I'm a big bathtub reader myself. I've never been one for reading on the toilet but to each his own.
When it comes down to a desperate moment, would you be willing to sacrifice the readability of your books in order to build a shelter? What classic tomes would form the strongest foundation for an igloo of literature anyway?
As a kid I always imagined having a dedicated space in my giant house just for reading and books. Of course I would buy this giant dream house with the millions I would earn working in the crayon factory I saw on an episode of "Mr. Rogers' Neighborhood".