This month's free e-book at University of Chicago Press is Reisman's book on BBB.
Link to Univ. of Chicago Press ebook of the month.
You give them an email address; they send you the link. I'm already on their monthly free ebook mailing list, so I can't say if you'd also have to join that list to get the freebie to download. I can say that I had no spam increase when I joined the list.
~CH.