I've written before about the different meanings of spirits. Mainstream Americans seem to think the word spirits means ghosts, but ghosts are only a tiny fraction of the millions of kinds of spirits that exist.
The Encyclopedia of Spirits: The Ultimate Guide to the Magic of Fairies, Genies, Demons, Ghosts, Gods & Goddesses by Judika Illes offers a much broader meaning of the term spirits, and describes 1000 well known spirits, from gnomes to deities.
I have just started reading the book, but so far it is thought-provoking, entertaining and very well written. It discusses the different spirit worlds in different cultures and the different kinds of spirits.
This is a big book, over 400 pages, and it's not just for shamanic practitioners. It is aimed at a general audience and discusses spirits from the perspective of many different spiritual systems, ancient and modern. Yet it is fun and easy to read.
The book was originally published in hardback but is available new only as a Kindle book---which you can read with free Kindle software on your PC, Mac, iPad, iPhone or Android phone or tablet. With the free Kindle reader software, you don't need to have a Kindle device.
The hardback version is available used for about $26 in the Amazon Marketplace.
I'll write a fuller review later, but for now, this is just a heads up in case you want to grab a copy of the Encyclopedia of Spirits or put it on your gift list. The Kindle version runs about $14.50.
You can download a sample for free, and it is a generous sample. So you can learn something just by reading sample. It is a big sample with lots of good text.