Thom Hogan's eBooks are very good. I have his D2h eBook, plus 4 others for my various bodies.
Thom will tell you everything you want to know about a D2h, and then some. His books are very extensive, perhaps too extensive for some people. Not a "Dummies" book. But he is very good at simplifying things down to what I consider a layman's level. He just spends 626 pages doing that
As I am sure you know, there are far fewer book options for those older cameras.