Not saying that this is the case for a second-but there is a possibility, given Rommel's later actions, that Irving paints him in an unflattering light precisely because of his political views.
BTW, the Heckmann book certainly "redresses the balance"-both in terms of the assesment of his qualities as a general and politically (if that interests you, at all. He was a confirmed Nazi and, like many other anti-Hitler conspirators, only got involved once he could see the writing on the wall).