This is very frustrating. My daughter has a Nook HD+ and some bn gift cards from her birthday.
Twice now, she finds a book on bn.com that she wants. It shows you can buy it as a Nook Book. We go into the SHOP (Nook) app, and it doesn't matter how you search for it, it cannot be found. We search every conceivable way, but cannot find them.
The first book was Quest for the Secret Keeper I by Victoria Laurie and the 2nd one, just two days ago, was The Name of This Book Is Secret by Pseudonymous Bosch. Neither can be found in the Nook App, but both are on bn.com as Nook books. Ultimately, we buy them online, but what gives? Is our Nook app broken somehow (but other books are there!) or is there a disconnect between bn.com and the content in the Nook Shop app?
It's not you, it B&N. See this thread for further discussion. It seems B&N has little interest in syncing the devices/apps with the website for shopping in any form.