The Demigod Diaries - Rick Riordan

What dangers do runaway demigods Luke and Thalia face on their way to Camp Half-Blood? Are Percy and Annabeth up to the task of rescuing stolen goods from a fire-breathing giant who doesn't take kindly to intruders? How exactly are Leo, Piper, and Jason supposed to find a runaway table, dodge a band of party-loving Maenads (who just might be a little psychotic), and stave off a massive explosion... all in one hour or less?
With his trademark wit and creativity, Rick Riordan answers these questions and more in three never-before-seen short stories that provide vital back story to the Heroes of Olympus and Percy Jackson books. Original art, enlightening character interviews and illustrated profiles, puzzles, and a quiz add to the fun in this action-packed collection that is sure to delight legions of loyal fans. (From Amazon.com)
This is a fun book! It includes some stories that have never been told and it also fills in some gaps between the Percy Jackson series and The Heroes of Olympus books. It had a few games in it, those were a piece of cake! Though I understand that it shouldn't be too hard for younger kids.
This book is considered to be a part of the Heroes of Olympus series, because most of the stories wouldn't make much sense unless you've read The Lost Hero and The Son of Neptune, and of course, the Percy Jackson series. 
It's a fun kind of random book, but I honestly don't see the point in owning it. The stories in here are not vital to the two series whatsoever. It's a fun read but not overly important. Not that I'm saying that Rick Riordan's books shouldn't be supported. I love his work! I am just giving my opinion on the matter.
Though I want to mention one story that was in this book. It is the last thing in the Table of Contents and it's rather long. It's kind of an after-the-Percy-Jackson-series story written by Rick Riordan's son, Haley Riordan who is/was 16 when this book was published. He's a really good writer like his dad already, though he definitely has a different style. Compared to his dad, I thought his writing was a little darker; if that's the right description. Rick Riordan's writing has always struck me as fun and a little bit silly, but Haley's seems more serious, not as funny, but it was still really, really good! 
Overall this is a fun book, but not very necessary. I enjoyed it but I don't need it on my shelf.
Title - The Demigod Diaries
Author - Rick Riordan
Series/Trilogy Title - The Heroes of Olympus
Pages - 242
Type of Book - Fiction
Website - http://www.rickriordan.com/home.aspx