If you bought ebooks from this ebookstore you should probably make sure you have downloaded a copy of your purchases. And just to be safe, you should probably also remove the DRM. This is the same advice I gave when Books on Board abruptly closed its doors in April, and it is just as valid today as it was them.
The only way you can really own the content you buy is if you remove the DRM and other restrictions that are placed on it. You can't have ownership without control, and you don't actually control a DRMed ebook.