My reactions to this book are...mixed (hence the average rating). First, the short stories. All three of them were excellent, expanding the story universe and giving more insight into the characters and their motivations. They laid the groundwork for some things that come up later in the series (and in the follow-up series) without bogging down the main narrative. The short stories were the reason I picked up this book in the first place.
Second, the interviews with the various campers and the other Camp Half Blood related stuff. I found these mildly entertaining, but not much beyond that. They do give some insight/information into the characters and how the camp works, but in general they feel pretty light.
Third, the puzzles and games. Again, mildly interesting, but also rather simplistic. This is completely understandable, given the target audience for the book, but I wouldn't have been fussed had they been left out entirely. I'm not a huge fan of puzzles in books anyway, since they can create issues if you lend/borrow the book.
Finally, the character depictions...no. Just no. They don't match up with my mental pictures at all
. Too cartoony for my tastes, with exaggerated proportions and garish colours. And there's just something off about the eyes in nearly every picture.