Jeff Kinney Calls His Latest 'Diary of a Wimpy Kid' Book 'Hot Mess' the 'Best Story' (Exclusive)

Jeff Kinney remembers the exact moment he realized how popular Diary of a Wimpy Kid had become.

It was 2009 and the author had just released The Last Straw - the third book in his series, which follows middle school student Greg Heffley as he documents his life in a journal. He pulled up to his book launch event at a Barnes & Noble in Long Island in New York, and was shocked at how many fans had come out to see him.

"I think there must have been 2,000 people at the Barnes & Noble and it was just absolutely overwhelming," Kinney, 53, tells PEOPLE in an exclusive interview. "My editor and I looked at each other and we knew that things had changed."