The Yale University School of Medicine Heart Book has a nice chapter about the heart and circulatory system.
Although the book has some outdated features and sections (published in 1994), it has a very nice chapter regarding cardiac anatomy, function of the heart and circulatory system in general.
You can read the chapter via the link below. It is excellent !
Reference:
The Heart: Anatomy and Physiology of the Heart and Circulatory System, diagnosisheart.com
http://info.med.yale.edu/library/heartbk/1.pdf