School Library Journal carries an article called 35 Going on 13: Teen Books for Adults in which the article discusses...ah...teen books for adults.
I've read three of the titles author Angelina Beneditti mentions and agree grown-up readers would be interested. I wondered if The Love Curse of the Rumbaughs shouldn't have been published for adults in the first place. Yes, Skullduggery Pleasant does have a very sophisticated adult--in a mannner of speaking--for mature readers to relate to. As far as Coraline is concerned, I wasn't crazy about it, myself, but its author, Neil Gaiman, has an enormous fan base that loves anything he does (while I just love some of what he does), so, yes, Gaiman's adult fans will want to read this book.