Yes, if I don't take notes on the first reading there won't be a second reading. Not much detail -- more than a page is a problem (this can be ameliorated though, see below). I make an effort to include points of particular agreement, disagreement and some projects to test the ideas (hopefully projects I actually want to do rather than mere 'toy' projects).

Now would be a good time to mention TreeSheets, which I feel solves a lot of the problems of more established note-taking methods (linear, wiki, mindmap). It can be summarized as 'infinitely nestable spreadsheet/database with infinite zoom'. I use it for anything that gets remotely complex, because of the way it allows you to fold away arbitrary levels of detail in a visually consistent way.