@shortboxed
Gene and crew, 3 of the last 4 books I've purchased through the app have become unavailable AFTER I've placed the order and paid, my payment being subsequently held for several days until I check in on a status. I am dealing with one of these scenarios as I type this, with my last order placed on 4/23 still in "processing".
Since the books are held by individual sellers there's no way to realistically monitor that all listings are in inventory or force a seller to follow through with a sale if that seller changes their mind. The only solution I can think of is to not process payment until the automated shipping shows the book actually being in the mail.
As it stands I have to assume that any books I show an interest in aren't actually available and I will only confirm as such by paying and seeing if the book ships.