I have the same problem being a student, I find it hard to keep track of the books I have in my accommodation and my house, but my general rule is : my favourite books on my bookshelf at home, books I haven't read yet I just stand up on my cupboard, books I don't want to throw away but probably won't read any time soon (like childrens books) in boxes under my bed, books for studying I either leave on my bookshelf at uni or if I need to bring them home I try to keep them in the bag I brought them home in and for any other books I use the top of my wardrobe as a sort of big shelf