Since the game is in the future, it seems kind of weird how you still have to carry around physical books. I suggest adding some kind of scanner item that scans a specified book in your inventory and makes it available to read on a PDA. The scanner would consume a certain amount of batteries depending on how big the book is and the PDA would also consume a small amount of batteries when reading, but it would let you read in the dark without another light source.
+1
I like the idea. “E-book” makes me think of having the player find book usb and load them into PDA, permanent books without the added weight, but cost batteries instead. But I like your proposal too.