How to download a Google play book Can someone tell me how to download a Google play book so that I can read it off line on my Android table which?

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
and
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 off line extension for ebooks.  I thought I had seen it as epub before.  So if that is the case, can someone advise me of how to convert the downloaded book to a way that I can import into my ebook reader library?

The ebook reader I use is: Ebook Reader

This is a clarification of the answer provided by DAN.

Important components of the answer:


The book is automatically downloaded and readable off line when
reading it online.
The download works the ACSM is a package of the download which can
be loaded on authorized machines for reading (via authorized
readers).


You can get the program for your MAC or Windows at:

http://www.adobe.com/products/digital-editions/download.html

For LInux you have to install Wine and run the Windows Version.

At present the latest Windows release doesn't work with Linux (Wine) you have to use version ADE17 for Linux:

Install Adobe Digital Editions on Linux

For the Android so for I find:

Aldiko Book Reader

I agree with Izzy's brilliant reflection that in the future I'll have to search for books that doesn't have this restrictions.
As the answer to Are Google Books DRM protected? explains, ACSM files are DRM-protected, so you can only read them in the Play Books app itself, not in another ebook app. Once you've "pinned" the book and it has downloaded, you can read it offline in the Play Books app.