I am very impressed and happy with these concealed book shelves. They were easy to install. They really look amazing on the wall. You will have to find the right combination of book sizes and weights to make sure they don’t sag a bit but that is easy to do. These are for regular size books. I tried some large books, but they don’t stick out enough. So books up to about 8 inches from the spine to the edge work fine. I will definitely buy more of these.