Look at his sources. He's read everything there is to read. He's really quite good. The Civil War is such a big topic, someone can be dead on and still have 20 scholars say you are "wrong."
I agree with some things VDH says, but I take exception to his putting Grant and Sherman on a pedastal. His view of Sherman is inconsistent with my views and many other historians/authors I have read.
He would have more credibility if he left the WBTS out of his writing, IMO.