Google Play has a promotion going on now in which you can receive 50% off of any, one, audiobook. It _appears_ that this 50% off is applicable to their _discounted prices_, not the full retail price.
I've seen ads about this all over the Google Play website (play.google.com) and Google's app. If, for some reason, you don't see any of the ads, go to the Google Play website. Click on the menu in the top left corner, select "Account," and then "Rewards."
I assume that this particular promotion is available to everyone, at least everyone who has an account with Google Play. However, I understand that some lucky souls (I am not, apparently, one of those lucky souls
) will have in their email inboxes an offer for a _free_ audiobook. This offer is _not tied to any trial or other audiobook subscription_. So, if you are not accustomed to checking your inbox very regularly, you might want to check it sooner than you otherwise would.
ADDENDUM: My source for the information in the third paragraph is a story in today's (February 3's) _Android Police_ website (
http://www.androidpolice.com/2018/02...e-google-home/).