I've read in several places that bookshelves have a maximum number of books they can hold, and I see some people implying they can hold more books but only show X number of books in the "read..." option.
I bought The Book Corral for one of my sims, along with some extra skill books (cooking 2 & 3, gardening 1, 2 & 3), and put them on the bookshelf, but my sim could not choose to read any of them. After discovering the above, I tried removing existing books from the bookshelf, but even with only three of its own books and the extra skill books the extra books never seem to show up.
I can't seem to find any explanation for this, is it the case that the shelves can only display the books they came with, and other books need the bookcase "opened" to get sims to read them? Is my game bugged? (Probably yes to the latter, as since I installed Island Paradise I can't even play the game without NRaas Overwatch)