Chapter marks (under each book) set where the progress bars mark chapters; needs firmware
v1.3.0+.
Send to reader works over USB in Chrome or Edge: plug the reader in and leave it on its Home
screen. Replace on reader writes over a book already there, keeping its file name so the reader
keeps its reading stats; your place may shift if the chapters were split differently.
Copying books another way? After replacing one, use Delete Book Cache in its menu.
Start from the original book when you can. DRM-protected books can't be optimized.