A Little Bit of Shamanism: An Introduction to Shamanic Journeying by Ana Campos is a wonderful introduction to basic shamanic principles.
Excerpt from the back cover:
Explore Shamanism with a Global View
Drawing from decades of training in Brazil and the United States, Ana Campos has written an overview of shamanism that is both personal and global. She provides an introduction to the history of shamanic methodologies, and provides guidelines for how to bring shamanic wisdom into daily practice. This book teaches why it can be important to establish a relationship with our helping spirits to assist the healing process. From alpha states to shamanic journeying, here is an insightful book for those looking to learn about shamanism.