Happy Hollisters and the Secret Fort

This book is the second installment in The Happy Hollisters series, which follows the adventures of the five Hollister children. While each book presents a self-contained mystery, reading them in order allows for a more complete understanding of the characters' ongoing development and relationships.

The Happy Hollisters series is notable for its emphasis on family cooperation and problem-solving, with all five siblings actively contributing to unraveling the mystery. Unlike some contemporary series that focused on a single protagonist or a smaller group, this series consistently highlights teamwork and the diverse skills each child brings to their adventures.