eBook Reader Download: Read EPUB, PDF and More

EPUB is the open standard most eBooks use, while Amazon's Kindle ecosystem relies on AZW3 and KFX. PDFs are common for technical books, and CBZ/CBR cover comics and manga. Before choosing a reader, check that it supports the formats your library actually contains.

• EPUB: the universal eBook standard, supported by almost every reader.
• PDF: best handled by readers with reflow or zoom controls.
• MOBI / AZW3: Kindle formats; Calibre can read and convert these.
• CBZ / CBR: comic archives, best in a dedicated comic reader.

Some tools, like Calibre, are full library managers that organise thousands of titles, edit metadata and convert formats. Others, like Thorium Reader or SumatraPDF, focus on a clean reading experience. Heavy collectors usually run Calibre for organisation and a lightweight reader for daily reading, while casual readers can pick a single all-in-one app.

If calibre is your choice, our step-by-step calibre download guide covers the current system requirements, which version older Windows and Mac computers need, and how to set up your first library.

"How to open EPUB on Windows" is one of the most common reading questions. Windows does not come with a dedicated eBook app, so the simplest route is a free reader:

1. Install Thorium Reader (from the official EDRLab site or the Microsoft Store) or calibre from calibre-ebook.com.
2. Right-click your .epub file, choose Open with, then Choose another app, and pick the reader.
3. Tick "Always use this app" if you want EPUB files to open in it by default.

If a book still will not open, check its extension. A file ending in .acsm is not a book but a download token from a store; see the next section. A file that ends in .epub.exe or arrives inside an unexpected archive is suspicious and should be deleted, not opened. Our guide to scanning downloads for malware explains how to check it.

Many purchased eBooks are protected by DRM, which limits the apps that can open them. Calibre's official FAQ explains that most purchased EPUB books have DRM that prevents calibre from opening them. When a store gives you an .acsm file, it must be opened in Adobe Digital Editions, which then downloads the actual EPUB. Thorium Reader supports books protected with Readium LCP, a DRM used by some libraries and publishers.

Kindle store purchases are best read in Amazon's own apps. Avoid tools or websites that promise to "unlock" protected books: they may breach the store's terms and are a frequent way to spread malware.

Look for adjustable fonts, line spacing, themes (including dark and sepia modes) and text-to-speech if you read for long stretches. Most modern readers also remember your position so you can pick up exactly where you left off.

Thorium Reader stands out for accessibility. Its developer, EDRLab, describes it as free with no ads and lists support for EPUB 2 and 3 (reflowable and fixed layout), PDF, DAISY accessible books and audiobooks, with settings for font, spacing, sepia and night modes, and columns. It is offered for Windows 10 and 11, macOS and Linux, and Windows users can also install it from the Microsoft Store.

If you buy or download books in a format your device cannot open, Calibre's built-in converter handles EPUB, MOBI, AZW3, PDF and more. Always convert from a clean original, and remember that converting heavily formatted PDFs to EPUB can require some manual cleanup.

Stick to the official vendor sites listed below and avoid sites offering 'free books plus a reader' bundles, which often hide adware. Calibre and SumatraPDF are open source, so you can verify the source if you want absolute confidence in what you install.