Even though it’s usually a mistake (grin) … do movies made out of books make you want to read the original?
Yes, all the time! Recently I picked up The World According to Garp, Revolutionary Road and a number of other novels after having seen the movies. One of my favorite reads, Henry James' The Portrait of a Lady, is one I read after seeing the movie and I loved it! The Wings of the Dove on the other hand, not so much! Another good one that I read after the movie was Edith Wharton's The House of Mirth.
I don't think it's a mistake! On the contrary I enjoy reading books that were the source for movies I liked; usually I like the books more but not always and sometimes it's just neat to experience the different interpretations of the story. Nothing wrong with that!