The book is in two parts: Pictorial Keys and Master Pages. The Keys are designed for easy visual comparison of details which look alike, narrowing the identification of a tree to one of a small group -- the family or genus.

Then, in the Master Pages, the species of the tree is determined, with similar details placed together to highlight differences within the family group, thus eliminating all other possibilities. The details of the Oak trees on this plate are an example of the system.

All of the more than 1500 photographs were made specifically for use in this book and were taken either in the field or of carefully collected specimens. Where possible, details such as leaves, fruit, etc., appear in actual size, or in the same scale.