> Reading books and trying to remember the maximum information seems rather pointless unless you're specifically studying for an exam or something. Your brain already optimises and retains the most relevant/interesting information for you.

That is just not the case. The brain does not work that perfect way. It tends to remember new info about stuff you already know a lot about.

That is whole reason for reading for retention is to hack the brain so that it remembers what I want to remember.