When you LOVE books as I do, every available space that you can find to showcase them is precious.
Consider the end of a hallway. Is there room on the far side of the last door in the hall?
Take this space and install some bookshelves! If you have a paperback collection, the shelving does not have to be deep at all, so even small amounts of space can store quite a number of paperbacks.
If you have a teacup or porcelain collection of some kind, utilize this 'found' space at the end of a hallway to showcase your beautiful items.
If your hallway is wide enough, consider putting shelving all the way down one side of the hallway if you really need extra space for books or accessories.
Every inch counts when you have more items than you have space for. Check out your hallways and see if you can't claim some otherwise under utilized potential storage space!