As to the first question, I think it depends on the subject matter. I may find it dry if a historian spent a lot of time talking about his or her research methods or something. On the other hand, if it is a subject that is personal to you or one which benefits from your commentary then that can be very interesting.

I majored in lit and I spent much more time with fiction but I view all writing as art. For me, the difference between good art and bad art is whether it generates a response in the viewer, reader, or whatever. Personally, I also like it when authors of non-fiction put a lot of effort into the sound and flow of their work and concern themselves with the entertainment of the reader. An interesting subject can be made boring and a boring one interesting depending on how they are presented.