I got this one for my birthday from my g/f (back in March) and didn't get to starting reading it until recently and now CAN'T put it down
The Rise and Fall of the Third Reich: A History of Nazi Germany by William L. Shirer
If you are not scared of 1200+ page book and this topic interest you, definitely don't miss it.
BTW amazon has it on sale now (my g/f paid the full price). For $20 it's a steal.
http://www.amazon.com/Rise-Fall-Thir.../dp/0671728687