I agree with tallchick. Books like you describe are good for getting ideas and some are good to give you an idea of how to make designs continuous. You already have quite a few that seem to do that. I found a lot of the books and guides I bought early on, I don't use at all and a few I never used.
Instead, you should decide what kind of quilting you want to get really good at. Say for example feathers. Seek out quilting bloggers who teach feathers. Or on line tutorials, (there are tons of them!) Then practice drawing them in the same manner you would quilt them. Before you know it you will be quilting feathers in every shape and direction
I don't think you should spend any more on books until you find out what style of quilting you really like, then, by all means, beef up your library.