Booking.com are running a promo where you can get $40 off a $200 hotel spend.
The $40 is credited back to your payment card after you complete your stay.
Strangely, there are no Terms and Conditions specifically for this promotion.
Only generic T&C found here.
Availability from 2017 to 2018
When you click the GO TO DEAL button, there should be a green promotional banner at the bottom of the page: