Young Cam Jansen and the 100th Day of School Mystery, Paperback/David A. Adler

Cam Jansen and her best friend, Eric, are excited about their class's 100th day of school partyTo celebrate, they're having snacks that start with the letter P: pretzels, popcorn, pineapple juice, and everybody's favorite, pizza. But when the pizza disappears from the kitchen, it's up to Cam and her photographic memory to "click" and solve this delicious mystery