I'm native spanish speaker and "bookcase" would be "estante" or "librero", "librería" is "bookstore"

biblioteca is more like a library. bookcase is a very vague word...

I agree that bookcase would be estante

bookcase is estante, not biblioteca.

Hmmm, well, for me biblioteca would be library, which in a house would have to be a whole room, estante would be the bookshelf and libreria would be the case in which some books were held. My dictionary says libreria is bookcase.