Shells are one of the habitats the first graders in my class study. We read fictional stories about hermit crabs and non-fiction books about many kinds of animals that live in shells. In this story, a young bear named Buddy, and his mom, go to the beach. Buddy asks all kinds of questions about how shells are formed. His mother gives very simple yet clear explanations. The book is easy to understand and my students learn a LOT! When we are done reading the book, I give each student a small handful of shells and ask them to sort the shells into bivalve and univalve groups. As we sort, we talk about how gastropods live in univalve shells. They also look for indications of when the mollusk had growth spurts. It is wonderful to see how much they understand and then to see them apply it.
Wallace has written other books, using Buddy as the main character, to help young children learn about their world. "Seeds! Seeds! Seeds!" and "Rocks! Rocks! Rocks!" are two especially good ones.