Koodo Reader is described as 'A modern eBook reader for epub, pdf, mobi, azw3 and txt, supporting Windows, macOS, Linux and Web. 1. Format support: epub, pdf, mobi, azw3, txt, md, djvu, docx, rtf, cbz, cbr, cbt, fb2, html and xml 2. Platform support: Windows , macOS, Linux and Web' and is an app in the News & Books category. There are six alternatives to Koodo Reader for a variety of platforms, including Linux, Windows, Android, Mac and Android Tablet. The best alternative is SumatraPDF, which is both free and Open Source. Other great apps like Koodo Reader are calibre (Free, Open Source), Okular (Free, Open Source), FBReader (Freemium) and Cool Reader (Free, Open Source).
Sumatra PDF is a slim, free, open-source PDF/DjVu/EPUB/XPS/CHM/CBR/CBZ/MOBI/FB2 viewer for Windows. Why another PDF reader? Sumatra has a minimalistic design. Simplicity has a higher priority than a lot of features. Its small and starts up very fast.
Calibre is a free and open source e-book library management application made by users, for users. Many languages, designed around the concept of the logical book, i.e., a single entry in your library that may correspond to actual e-book files in several formats.
KOReader is a document viewer for E Ink devices. Supported fileformats include EPUB, PDF, DjVu, XPS, CBT, CBZ, FB2, PDB, TXT, HTML, RTF, CHM, DOC, MOBI and ZIP files. It’s available for Kindle, Kobo, PocketBook, Android and desktop Linux.