That sounds like the epub has an error in the .ncx file, and that's because Moon+ uses that exact file to organize the chapters in the reader.
You should check the .ncx in your .epub (you can do that with any text editor app like notepad++ or your windows Notepad, or use Calibre).
Check that Chapter 2 leads to chapter2.xhtml and chapter 3 leads to chapter3.xhtml.
The problem should be chapter 3 from what I read from your post, it may be leading to chapter2.xhtml in your .epub
Edit: Also check toc.xhtml the same way, just in case.
I upload all my ebooks to Google Drive, and only have a few in my Google Play Books library at any one time.
Play Books lets you read online from a browser on any device without downloading the book, and saves place between devices, so it is far and away the best choice for me. You can also add epubs straight from your Drive, so you don't have to download then upload something to add it to your library. I like its read aloud function as well. It's organizational abilities are really lacking, though, so I don't keep everything I own in there, just what I'm currently reading or may read in the near future.
@mortcs Please contact Amazon support, as they are the ones who can push the full book to you. We have already e-mailed asking them to push it to all customers who bought the book, but as an individual customer you might be able to get a more timely response by contacting them yourself.