Incredible guide
This little book is an incredible thing.

It is tiny enough to fit easily in your pocket, which to me means that it's going to get used more often.

The method it takes you through to identify the various trees is great. It is extraordinarily simple.

Tree Finder: A Manual for the Identification of Trees by Their Leaves (Nature Study Guides)
This is a great, easy to use tree ID guide. For being so small it includes a wide variety of common trees and provides helpful information for good identification.

Oldie and a goodie
I remember using this little book back in 1984 or so for a leaf project for my eighth-grade science class. The whole class got one. I decided to get one for each of my kids since we like to hike. It wasn't as easy to use as I remember (so my elementary-school age kids had some trouble using it), but it's still pretty neat how the book will ask you a series of "does it look like this or like this" type of questions to help you narrow down to the tree you're trying to identify.

An excellent way to identify trees
I have used this guide (and also the "Winter Tree Finder") for decades and find it accurate and easy to use for it's intended purpose: identifying what tree one is looking at. If you want to learn more ABOUT the tree, get an additional book like the Audubon Society publishes. But this is so convenient to carry and easy to use it's almost always with me when I'm out hiking.

Handy reference
This book provides good coverage of most trees of the northeast. It is compact and handy to carry along.