Historical Dictionary of Shamanism, 
by Graham Harvey 

PDF, 329 pp.

This is from the "Historical Dictionaries of Religions, Philosophies and Movements" series. 

Shamanism (a practitioner is a shaman) is a range of traditional beliefs and practices concerned with communication with the spirit world. There are many variations of shamanism throughout the world, but several common beliefs are shared by all forms of shamanism. Shamans function as intermediaries between the human and spirit worlds. They can treat illness and are capable of entering supernatural realms to provide answers for humans.

If there is any interest, I have another reference book as well as audio (lessons and drumming) that I'll upload. You can show interest, of course, by downloading and seeding... please!

Check my torrents for more reference books on spirituality and other topics.

For an introduction to shamanism, check the Wikipedia article (quoted above) - 
http://en.wikipedia.org/wiki/Shamanism

Also, I found an introductory audio at archive.org that you can stream or download - 
http://www.archive.org/details/ShamanismTheOldestInwardPath