24 Graded Exercises for 3-string Guitar

From the introduction:

This book is an introduction to the basic language of American traditional music and how it lays on a 3-string fretted instrument. You will recognize the familiar sounds of blues and folk in the pentatonic scales and the simple rhythm patterns. It also explores the accessible keys for the G-D-G tuning, introduces multiple options for chord voicing in each one, and begins to explore how applying different picking and rhythmic approaches can evoke other instruments.

Skilled guitar players will find the lessons rudimentary but helpful for navigating the 3-string neck and solidifying the vocabulary. Beginners will find them accessible and straightforward. Regardless, the main purpose of this book is to demonstrate one set of possibilities, and equip the player to be able to continue the exploration on their own. It’s not meant to be comprehensive, but a useful overview.