He has turned his course text into a free book at:

http://bookboon.com/uk/student/it/an...atabase-theory

It is rather unique, being more self-contained and therefore
approachable than many other books on the subject, also short and
unconventionally daring in places. Most of all, he takes a lot of care
to emphasize the logical basis of the theory and how it connects with an
implementation language.