There are two ends to optimize here; you can focus on selecting the best things, or focus on getting rid of the worst things. I used to read way too much news, for example; and after reading something good I'd usually go on to read its comments even if I knew (or would have known if I'd thought about it) that they wouldn't be worth it. Before deciding which of two good books to cut, install a time profiler like RescueTime or ManicTime to make sure you know where your reading time's really going.