Is it an adaptation, a variation, or a a retelling

I love reading books that are based on book from classic literature. Such as Jane Austen, the Bronte sister's, William Shakespeare, ETC. O n e of my favorite authors for that is Claire Lebzebnik. But by my reading of the book, I couldn't tell ya if it is an adaptation, a variation, a retelling, or something else. Any insight or suggestions?