Amazon sent the following information:
"We’ve sent an e-mail to customers who own the book to notify them of the update. These customers can download the update through their “Manage Your Content and Devices” page."
March 31, 2016
Pre-order RTL-SDR book customers were delivered the wrong book by Amazon. You got the Pi 3 book for reasons unknown.
The RTL-SDR book will be sent out in the near future, as soon as someone at Amazon bothers to read my emails and presses a button.
This might take a while, as Amazon publishing customer service is worse then customer reps for my cable, Net subscription and car insurance combined.
The Amazon order page shows the correct version, the hiccup only affects pre-order customers.
Even thought it's got nothing to do with me, I'm terribly sorry and apologize to all pre-order book customers.
I sincerely hope that you'll get the book ASAP and will enjoy reading it as much as I enjoyed writing it.