Cass Sunstein has a useful post on the idea of the “unitary executive” at the University of Chicago Law School blog. the aim of the post is to explain what the debate over the unitary executive is — and is not — about.
The most important point is that the claim for the unitary executive is not a general claim about the President’s power to act on his own or to contradict the will of Congress. You can believe in a strongly unitary executive branch while also believing that the President cannot make war, or torture people, or engage in foreign surveillance without congressional authorization. You can also believe that the president can do a lot on his own, or a lot in violation of Congress’ will, while also accepting the view that Congress can create independent agencies and independent prosecutors. In short, the debate over the unitary executive is an important but narrow one, and it is a small, distinct subpart of the general debate over presidential power.