Say you just bought an Amazon Kindle or a Barnes and Noble Nook. You want to convert your eBook collection to .EPUB or .MOBI format. For this, install Calibre. The application not only provides you with a graphical way to manage your eBook collection, but also comes with a set of useful command-line tools. One of these is ebook-convert. This tool can help you convert between tens of standard formats like EPUB, FB2, LIT, LRF, MOBI, OEB, PDB, PDF, PML, RB, RTF, TCR, TXT, HTML and more. Even CBR and CBZ (comic book formats) are supported.

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Convert eBooks in Linux