Diary of Greg Heffley's Best Friend

 by Greg Heffley's Best Friend Rowley Jefferson is a short story/spin-off book released in October 2018 to Scholastic Book Club subscribers (or Teacher Advisors) and then on 28 February 2019 in the UK for World Book Day.

The book focuses on Rowley's relationship with Greg Heffley from his point of view. An expanded version was released on April 9th, 2019 under the name of Diary of an Awesome Friendly Kid: Rowley Jefferson's Journal.

Chapters

 * 1) Early Life
 * 2) The Stuff from Fourth Grade On
 * 3) An Even More Scary Story
 * 4) The Time I Saved Greg From Tevin Larkin's Birthday Party
 * 5) The Time Greg and Me Dug Up an Ancient Burial Ground
 * 6) The Time Greg Played a Hilarious Prank on Me
 * 7) Another Time Greg Got Mad At Me
 * 8) The Time Me And Greg Had a Double Sleepover
 * 9) The Time Me and Greg Did Some Comics and I Had To ___ The Cheese
 * 10) The Adventures of Greg and Rowley

Trivia

 * stated the book could be used to showcase different kids' points of view on things, talking about friendship along with its "silly humor".
 * The World Book Day edition also features a sneak preview of Sam Copeland's "Charlie Changes Into A Chicken" at the end.

Characters

 * Rowley Jefferson
 * Greg Heffley
 * Susan Heffley
 * Linda Jefferson
 * Frank Heffley
 * Robert Jefferson
 * Manny Heffley
 * Rodrick Heffley
 * Tevin Larkin
 * Joseph O'Rourke
 * Scotty Douglas
 * Bill Walter
 * Two unidentified teenage bullies
 * Carrots
 * O’Rourke’s Dog
 * Bampy
 * Creighton the Cretin