I read all of them, all from internet in date order from oldest to newest:

1. John Doyle, Bruce Francis, Allen Tannenbaum: Feedback Control Theory,
Published by Macmillan in 1992,
http://www.control.utoronto.ca/people/profs/francis/dft.html

Nice theoretical overview of significant ideas in robust theory; norms,
derived formulas on robust stability and performance, loopshaping (robust
in frequency domain).

2. Michael Lemmon: Lectures in Robust Optimal Control, Dept. of Electrical
Engineering, University of Notre Dame,
http://www.nd.edu/~lemmon/courses/ee555 /

Mostly theory and theory but then, suddenly, really nice loopshaping
examples.

3. Okko H. Bosgra, Huibert Kwakernaak, Gjerrit Meinsma: Design Methods for
Control Systems. Dutch Institute of Systems and Control,
http://wwwhome.math.utwente.nl/~meinsmag/dmcs /

My favourite. Theory with many valuable conclusions.