“The file is an EPUB document, and odds are you don't have a program on your computer that will install the file. Luckily, you can use Google Play Books to your advantage here.” Facebook · STRYD Community · 3 years ago

A highly recommended free software for PC/Mac that lets you organize, convert, and read your library. Managing and Troubleshooting

If you see "(Untitled)" in your Table of Contents, it is usually because the source file is missing a header for that section.

“although epub would be great for novellas and so on... I dont think Strategy guides or other not quite "booky" products would be great... as you'd usually want to keep color and everything displayed” Obsidian.net · 13 years ago

If the book has many images or a specific magazine-style layout, EPUB may occasionally struggle to keep everything in its exact place compared to a PDF. Reader Perspectives

You can upload the file to Google Play Books via a web browser and then read it on any device with the app.

Often recommended for maintaining complex formatting that other apps might "screw up".

Since EPUBs aren't native to most computer operating systems, you'll need a dedicated reader.