Check out the AMSA website. They have a really good report (several pages long) outlining all of the different aspects of managed care. I think it's called Managed Care 101.
Do a search of this site for HMO's, interview prep, interview tips, etc. and you'll find a ton of stuff. We've kind of been over this a lot.
I do have a recommendation for a book that's not been mentioned yet that purports to get at the root of the problems with the U.S. health care system. It's The Grand Disguise: Fifty years of faulty thinking nearly ruined American medicine, but a remedy is possible. A practicing Doctor's Analysis of Healthcare. Whew!! Longest title I've ever come across. The author is William C. Waters III, MD, an internist/nephrologist and clinical professor at Emory. Milton Friedman, the Nobel Laureate in Economics says of it
[This] analysis of what is wrong is I believe entirely correct. ••