Have you ever encountered the following scenario:
You: I just read a great book!
Friend: What’s it about?
You: (paused and tried so hard to recall what you’ve read)
Or have you forced yourself to finish a book in a day or so, because you worried you would forget the previous chapters after a reading hiatus?
When it comes to widening our knowledge base, unfortunately, we usually prioritize quantity over quality. Yes, the more you read, the more information you get, but we tend to forget the things we read after a short period of time. Our inability to retain information from what we have previously read is dauntingly common. We sometimes skim through the passages; or read word by word, letter by letter, without understanding the content; or even scan the book and get to the next — to bombard ourselves with piles of knowledge. But how often does loading and stacking help us retain what we read?
If we can’t remember anything from the books we read, what’s the point of reading? To make your reading effective and meaningful, here are

4 strategies to help you retain what you read:
1. Generate questions and look for answers
One reading habit we have is to completely immerse ourselves in the text and drill into the details when we read. We think the best way to get the most out of a book is to complete all of the chapters, but we don’t always remember the walls of text upon closing the book. One method to retain our memory is to first go through the table of content (the table of content is here for a reason!) and generate a list of questions, then actively search for answers in the book. When we have a purpose to read a book, it is easier to find and remember what we read.

2. Scribble in the margins while reading
Jotting notes is definitely a great strategy to better knowledge retention. When a certain paragraph stands out to us, we will usually highlight or copy the text, but instead, we should use our own words to summarize key ideas to make a stronger impression. Through this process, you are teaching and explaining to yourself on the points. If you are able to give an outline of the passage without hesitating, you can ensure you have really comprehended and digested the content.

http://mystudyfocus.com/articles/4-effective-strategies-to-remember-everything-you-read/