Amulet Books today announced details of the fourth book in Jeff Kinney’s hit illustrated kids’ series about supposedly lame middle-schooler Greg Heffley. The new book, Diary of a Wimpy Kid: Dog Days, is due in stores Oct. 12 with a first printing of 3 million copies. Since the publication of the original Diary of a Wimpy Kid in 2007, more than 20 million copies of the series are in print in the U.S. The third book, The Last Straw, was released in January of this year. “I didn’t want my fans to have to wait a year for a new book,” Kinney said in a statement. “I’m very excited about Dog Days, because it takes Greg out of the school setting for the first time. It’s been a lot of fun to write about the Heffley summer vacation.”

This week, Fox 2000 also announced the casting of Zachary Gordon (National Treasure: Book of Secrets) in the title role of the movie version of the first book. The live-action film is tentatively scheduled for release in April 2010.