There seems to be this obsession with quantity over quality, when it comes to reading books. I fall into this trap all the time. The reality is though, there is a very limited amount of time and so far better to read a handful of great books and retain the good advice, than read loads and loads of books and remember nothing. So the first thing I suggest is if a book is good enough to read it once, then you should really read it again. You'll be amazed how much more of it you can retain because you have much better context.
Whenever I read a book, I always highlight anything that stands out. If it's a physical paperback, then I always use a highlighter pen everywhere I need to. If it's my kindle it's a little easier as I just use the highlight feature. Either way, it's really worthwhile to spend the time reviewing your highlights and writing up your own interpretation of why it's important to you. This can be time consuming and comes back to my first point...you probably won't be able to read as many books as you'd like each year but once you've written up your notes and ideally published them online or evernote or wheverer. That should be it forever, you can refer back to it whenever you like and usually only takes 20minutes to read over your notes versus 7/8 hours reading an entire book!
Thinking about it, I don't really do this much as I'd like! I do almost always go and read other peoples summaries and reviews as I find it helps with my retention and anything I might of missed. But as well as that, you really want to read more around the subject, see other peoples perspective on it and deepen your knowledge.
I can't remember exactly what the old adage is but it's something like learning by doing or you really learn when you teach others what you've learn't. I don't go around teaching people about a book but I do talk through things I've learn't with my girlfriend and when there's something I can't quite explain or perhaps having understood myself, I know to go back and check my notes or re-read a few bits.
There's nothing more satisfying than keeping a running list of what you've read and when you read it. It helps highlight how much or little you've read and how consistently you're doing it. I don't actually have a great method for doing this at the moment, some of it is in Goodreads, some of it is on my blog and some of it is in a new tool I've been using called notion. I need to sort that out but what . I really need is a timeline somewhere of all the books I've read and when I read them. The closest I have to that is my reading list.
To be honest, I'm in a constant battle to fight the resistance telling me to stop reading. But it's actually a good thing to take a bit of a break from a good read. Time to reflect on what you've read and put into action the things mentioned above like writing up notes, sharing what you learn't with other people and reading other articles on the topic.
By Jonathan Clift, a UX Desginer based in the UK.