typography - Designing for a 6in x 9in book

I am putting a text heavy book together, 6in x 9in paper size. (Perhaps related are this and this link.)

Now I look for good font pairings (nice examples are here) and margin settings and line spacing that works well. My current settings are 0.8in top/bottom margin, and then 0.8in inner and 1in outer margin; line spacing 1.3.

What are recommended approaches here, how can I set up visually pleasing pages?

EDIT: I would like to have a clean and simple feel to the book, while the text is readable comfortably. Almost leaning towards sans fonts although I'm not too sure if that makes for good reading comfort.

EDIT: After posting this question and receiving heaps of good comments, I started reading the book "Elements of Typographic Style" which gives answers to pretty much any question this thread raised, directly or indirectly. I'll post whatever typefaces and page settings I chose later...