How to download ebooks from Google Play Books for offline reading on other ebook reader apps?

I use Ebook Reader . I attempted to use the download option on the MyBook list (the three dots). The file that came was incompatible with my ebook reader. It was: Warriors_2_Fire_and_Ice-epub.acsm I tried renaming the book in various ways such as: - Warriors_2_Fire_and_Ice-epub - Warriors_2_Fire_and_Ice.epub However, I couldn't import either of those files into my ebook reader. The extension .acsm might be the offline extension for ebooks. I thought I had seen it as an epub before. So if that is the case, can someone advise me on how to convert the downloaded book to a way that I can import it into my ebook reader library?