Moved your post to its own thread.
Books must have a Unique Title - Author or they can be considered Duplicates. Adding a number is a good way to tie break
The FILE NAME (send template) must resolve as unique. {title}-{authors}
usually has it covered. If you use the sort field in the template, be sure the the *_SORT field in the MDE is not red. (
the Quality check plugin has checks to help locate these issues)
For some devices, this must be EMBEDDED into the book. If you just copy (using the OS) this never happens (the device transfer plugin does this).