Thanks for all of the interest in this. The response has been overwhelming, and I won't be able to reply to everyone individually.

So here is a thread of exactly what happened (illustrated!), and I'll keep it updated.

The problem first appeared last week, when I attempted to open a book on my Kindle.

The book cover appeared in my Library as normal.

When I tapped on it, the following message appeared:

I then checked through my Kindle and found quite a number of books that generated the same error.

Then, I checked my order history and found other books I had forgotten about, but did not even appear on my Kindle.

The original orders still exist for all of them in my Order History. However, many of them are not available in my Digital Content Library.

The books are still available on Amazon (i.e. they have not been withdrawn by publishers or authors).

The total is 66 ebooks.

Once I discovered this, I contacted Customer Support again. This was a long and comprehensive chat, trying out many different options for recovering the books, synching etc.

The result was this:

I have trawled my order history and have the Order Num for all of the missing books.

My next step is to go through this process for maybe 5 books, and gauge how practical it is going to go through the process for every one.

It's frustrating of course, but I am not angry at the Support folks (who undoubtedly have been doing the best they can), or publishers, or the authors.

It looks like these books have fallen between the cracks of the Kindle ecosystem somehow.

I have successfully re-purchased, and had a full refund for, the book I first noticed was missing.

The process took 8 minutes, between buying the book, logging in to chat again, and detailing the issue.

Just 65 other books to go! No doubt there will be efficiencies if I purchase batches of books. But realistically there are several hours ahead to get through this.

[Edit: I was informed in a subsequent chat that there was no refund - see attachment]