Yes, you can publish your book on Google Play Books even if it's already
published elsewhere. Google Play Books allows authors and publishers to
distribute their books on the platform, even if they are available through
other retailers or self-publishing platforms.
However, you should ensure that you have the necessary rights and permissions
to distribute the book on multiple platforms simultaneously. Some publishing
platforms may have exclusivity requirements, so it's important to review the
terms and conditions of your existing publishing agreements.
Publishing your book on Google Play Books can provide additional exposure and
reach a wider audience, allowing readers who prefer the platform to discover
and purchase your work.