Kobo

ACSM stands for “Adobe Content Server Manager” and refers to a file format used by Adobe Digital Editions, a piece of software used for managing and reading ebooks. What is an ACSM file really? ACSM files are used to download and activate ebooks from digital libraries and online bookstores such as the Rakuten Kobo Store. When an ACSM file is opened with Adobe Digital Editions, the software contacts an Adobe server and uses the information in the ACSM file to download and unlock the corresponding ebook, which is then saved in the EPUB or PDF format....

When using Linux and buying ebooks, you will have to convert ACSM files on Linux to ePub. The Kobo store and other popular ebook stores don’t just give you a usable ePub, they often come in ACSM format. To actually read the book you’ve purchased you need to open that ACSM file up in Adobe Digital Editions and download an ePub. Then if you want to do anything with your book, like put it onto your own e-reader, you’re going to need to remove the DRM....