I haven't seen it cause problems, but if you have a low end system, it could be just one of many small things that add up. It will probably make your save file bigger, though I couldn't say by how much. Also, if you buy out the consignment store a lot, the same thing could happen, as the game generates books written by other sims to go in the store inventory. These will also all appear in the library. Really though, if small things like this that are a part of normal gameplay are causing problems, then you may need to upgrade your system.