Crown Book

Full-screen large text file reader on your watch.
One book at a time in a loop (the book can be read continuously).
Font size matches system settings – it can be changed while reading in the watchOS Control Center.
Sending another book to the watch replaces the current one.
Splits large files into pages and remembers the last page read.
There are page-turn buttons at the beginning and end of the page.
Tapping the system clock moves you to the top of the page.
! The book is not included with the app.

Sending a file from iPhone to Apple Watch:
UTF-8 encoded .txt format (you can use TextEdit in macOS to change the encoding).
.txt compatibility with Apple Pages: File - Export to - Plain Text... - Save.
! When sending a file from iPhone, the Apple Watch must be unlocked with the app running.
! If the text doesn't appear on your watch after uploading, try again until it succeeds.