A human brain does not forget things, per se. Everything that we do and say is stored somewhere in our subconscious in some context. Just like the RAM and the HDD on our computer systems: the RAM is useful for quickly recalling functions and commands, while the HDD stores information that is not regularly used.
Anyway, about your question (this question was answered by me on Quora, which can be found here: Answer On Quora), first ask yourself if you would want to remember all your readings to be able to access it in a quick manner. If yes, then that would mean clogging your mind with information that you may not need on a regular basis. I would recommend this: try remembering only information pertaining to your field/career. This would be information that you may need on a regular/occassional basis. About all your other readings, make an organised diary/notebook with important points written down from the books and articles that you read. Enjoy reading!