For anyone looking to get a very detailed understanding of the mortgage industry, I recommend checking out this section on the Calculated Risk blog entitled "The Compleat UberNerd". It offers a very comprehensive (and lengthy) write-up on several areas of the industry that many people misunderstand or just don't know much about. This probably isn't for everyone; in fact, they even go ahead and say:
an “UberNerd” is someone who is compelled to understand how things work in grim detail, even if the things in question are tedious in the extreme, like mortgage insurance policies. Not everyone who visits the blog is an UberNerd, or aspires to UberNerdity, but on the other hand those who display UberNerditude in the comment threads are treated with a respect bordering on lunacy.
I guess I would qualify, because I find all of these posts very interesting.