It is surprising how many people will tell me that they do not know what the dials and buttons do. But want to do something in particular and if I suggest that the get the manual out to find the section they give me a blank look. What manual?? Once they figured out where to put the batteries and how to turn it on the manual got lost somewhere in a drawer.
The original question was
Having moved up to a DSLR, I need help in understanding this level of photography and would like to read more about it.
and so a book like "Understanding Exposure" would be the answer.
I really feel that the manual is a great help. Once I knew what EV did and after looking at examples of changes in EV I needed that manual to find how to change the EV.
It is good to know the manual backwards and forwards. I am not knocking the books like "Understanding Exposure" at all. In fact, I just called my wife and asked her to look for it at the library (helps that she is the research librarian there) and to bring home something else to explain composition and so forth.