I sometimes take notes on books I read. I love having notes; usually, I forget a lot of the details within 6 months (though most of the nonfiction I read is technical learn-about-a-subject from this rather than "here's life advice," as another commenter pointed out, the latter is only useful up to a point). However, the compulsory need to have notes itself makes me read less, because I don't like doing it, so often I don't take notes. Instead I write a lot of commentary in the margins, underline things, etc, as a compromise. That way I can easily skim back through my annotations at a later date if I want to. But really, electronic notes are ideal.