This book is a good introduction to understanding the parts, structure, and meanings of the Tipiṭaka. Tipiṭaka is the Pāli word meaning "Three Baskets" used to describe the body of discourses and teachings (in three categories) credited to Siddhartha Gotama, or the historical Buddha. It is also called the Pāli Canon. Specialized monks memorized his stories and discourses for centuries before coming together to put them into one body of work.
This is an overview of the three baskets of knowledge, namely Vinaya Pitaka - rules of conduct for monks, Suttanta Pitaka - the collection of discourses delivered by the Buddha and some of the chief disciples + various narratives concerning different aspects of Dhamma, and Abhidhamma Pitaka - an analytical approach to Dhamma and its constituents. With very little concrete exposition of the Dhamma, this book is a map of the literature available to the practitioner, helping one to navigate the vast ocean of Dhamma knowledge.