This one is specifically stolen from Paul Graham.
Since, I exclusively read non-fiction, I always think that I should be mentally super responsive and focused when reading a book, otherwise I can't absorb every word and thought of the book. Same applies to seemingly important articles.
That hasn't changed 100%, but I am reading more than before.
He basically said that the only thing that matters is that you read. You usually only take 2-5 things with you from reading a book. And that is ok. As with making decisions, your brain is not designed to handle so much overload. And while you 'only' (your vocabulary) remember some main points, your brain still gets stimulated the whole time and the perspective of others will influence how you see the world.
So, while you might forgot more than you take away from reading something, you have still read it and your brain expanded a bit. It wasn't enough yet to brake the wall down, but you did the first step. The next time a similar information comes to that area of your brain, the first path is already paved and it is easier to stick. And if it doesn't stick this time, it will the other time. And if it never sticks, it probably isn't that important to you.
Another angle how to view it: have you ever met a successful person who doesn't read extensively? Probably not.
I'm going to bed and finish my 10 pages before sleeping. (btw. atm reading: 'What got you here won't bring you there')