I have an exclusive coupon code that will give you 40% off all Rocky Nook books, including the new Nikon Z6 and Nikon Z7 books (pictured above):
Use coupon code NikonRumors during checkout and you will get 40% off your entire order.
The above coupon code is valid only for rockynook.com (make sure you make your purchase from any of the Rocky Nook links in this post).
All available Nikon related books can be found here and here.
Rocky Nook books are also available for sale on Amazon, but in most cases you will get a better deal if you use the above coupon and purchase directly from Rocky Nook.