As far as I can tell, once you read a book and the benefit is all used up, the book stays in your possession but is now nothing more than a random keepsake which can't be used again, nor can it be gifted or sold. I have a couple of questions:
a) Can I dump a read book and when it is found can it be used by another person who finds it?
b) If I get rid of a book and the same one appears on a Duke Mission to buy, can I read it again for the benefit?
c) Can I read more than one book at a time to "double up" on benefits? Ie: one book to increase my gym benefits and one book to increase the amount of energy from cans.