I highly recommend people to read at least one book for pleasure one book for personal growth, and one book to educate yourself every month. I like to read adventure, anime, pretty much anything for my pleasure “book.” The Attack on Titan manga has been a choice of mine. If you forget history we’re doomed to repeat it so I recommend taking a trip through history with some thing like The Gulag Archipelago. Last but certainly not least, my personal favorite self help book is 12 rules for life: An Antidote to Chaos, by Dr. Jordan B Peterson.
I think that's a great way to stay sharp!