I see a lot of "almost" bookshelves. They hold books and look "design-y" but they waste energy and space. If you are really into books, it's not about the cute shelves. It's about the books. Make that space hold as many as it can.
We've used a similar corner shelving unit to create space in a small 7 by 9 ft room. It's a great, easy shelving solution for small spaces (although installing it was a bit tricky as the walls weren't plumb.
Floating bookshelves, these are bookshelves I like. Looks like you could do this with an IKEA kitchen wall cabinet minus door and turned horizontal to mount. IDEA for narrow wall next to our kitchen wall