David R. (University of Aberdeen, Scotland, UK) Green 
GIS [PDF ebook] 

In a relatively short time Geographic Information Systems (GIS) have spread from being primarily a research tool to higher and subsequently secondary education, and from the researcher to the user. GIS: A Sourcebook for Schools is an easily accessible guide to GIS at an elementary level and provides sufficient background in GIS to ensure a comprehensive working knowledge of the subject. It is written specifically for schoolteachers looking to incorporate GIS into the secondary school curriculum, and will be the essential textbook for all those wishing to gain an introduction to a working knowledge of GIS.
The book contains everything that a teacher wanting to implement GIS into the curriculum would need, including glossary of terms, explanation of the fundamentals, definitions and further reading. No other book will be quite as useful as this one.