Cannot Open a Book on the MacBook

So I bought a book. Started reading it on the iPad, then went to get some work done on the MacBook. Decided the book was better (who cares about work right now?). Opened the Books app... annnnd

Well am I supposed to keep a track of what format the book is in? When I downloaded it I didn't care. Nor did it tell me.

Checked online for solutions like any good paying customer should, and I:

• Removed the download, and downloaded it again. No luck.
• Removed the download, signed out of the Books app (iCloud I suppose), signed back in, and downloaded it again. No luck.
• Found the download location: ~/Library/Containers/com.apple.BKAgentService/Data/Documents/iBooks and it turns out that it's an ePub. Ah finally, now I know the format. Deleted the book from Finder, downloaded it again. No luck.

So I'm considering downloading an ePub reader that is NOT the Books app. Move all my purchases there and hopefully it has a decent file manager. Then each time I buy a Book from the Books app I move over the book into this new reader. This making me crazy.

The other thing is maybe I can use the Kindle app.

Or maybe there is another less drastic solution I haven't considered?

Hope someone can help.