I read a bit of a book in Uni but cant remember what it was now. IT was about whether Hitler was in charge of Germany during the War or if the Nazi Party Machinery had taken over and had a momentum of its own. Im tearing through Evan's trilogy at the moment and it seemed like it would answer some questions and refresh me on some stuff I learned at Uni.
You must read Ian Kershaw's The Nazi Dictatorship: Problems and Perspectives of Interpretation. Kershaw arranges each chapter by subject and summarizes the main scholarly points of argument about them (for example, in his chapter about the Holocaust he presents scholarly arguments over whether or not the Holocaust was an intentional policy from 1934 or an event that arose from unplanned circumstances) before concluding the chapter with his own perspective.
I believe there is an entire chapter dedicated to the exact subject that you're interested in, but IIRC it really permeates the book and comes up in the Holocaust section as well. This book is indispensable if you want to learn about recent scholarship about Nazi Germany and should give you enough information to draw your own conclusions.
Haven't read these in a while, but you might want to try:
M, Geyer, “The Nazi State Reconsidered” in R. Bessel, ed., Life in the Third Reich (1987)
M, Broszat, The Hitler State. The Foundation and Development of the Internal Structure of the Third Reich (1981)
Mazower, Mark. Hitler's Empire: How the Nazis Ruled Europe (2008)
(I think Mazower might be the best out of these three)
I must say, I really loved the Evans trilogy! Great place to start for these kinds of things. If you are interested you might also enjoy Tooze's "Wages of Destruction" which talks a lot about how economics and not Hitler determined certain aspects of Nazi foreign policy.