Spineticklers is a series of books that appear in Diary of a Wimpy Kid: Double Down. It has been read by Greg Heffley and other kids at his school. The author of the book is I.M. Spooky and there has at least been 97 books in the franchise. There is a junior series, for Kindergartens, but is read by Rowley Jefferson, because he is too scared to read the regular series. (Although he is still very scared of the junior books, and even wrote a letter to I.M. Spooky about how he wanted the latter to make the books less scary.)