I have a Nook and I currently have 47% available storage, I only have one book currently checked out. Why is the amount of my storage so low?
Thanks for your question! To give a better answer I'll have a couple of additional questions for you: First, what model of Nook are you using? Is it an e-ink reader like the Simple Touch or one of the newer, Android-based devices like the Nook Tablet or the Nook HD? And do you mind if I ask for your library card number so I can check on the title you currently have checked out?
Generally, the files for individual ebooks are not huge, at least not by the standards we're getting used to these days. One thing that may be affecting the available storage displayed on your Nook is that Barnes and Noble reserves some space on the device for their software and material purchased from them. See this forum for one example. If you're using one of the Android-based Nooks, you might check through your apps to see if one of them might be improbably large.
I'll be happy to help you troubleshoot as far as I can; at the end of the day I think it's most likely a product of Barnes & Noble's reserved space or other things particular to your Nook, but if your library book is eating that much room I'll try to figure out why. Let me also recommend Overdrive's technical support page; there might be some advice there that I'm missing.