Books reach the Bookshelf three ways: files you add, an OPDS catalog, and your library hub over WebDAV. You can use all three at once.

Files on the device

Tap Add a book on the shelf and pick a file. EPUB, CBZ comic archives, PDF, MOBI and FB2 open in the reader. On iPad the app’s Documents folder is visible in Files, so you can drop books in there too, or point the shelf at a folder of books you already keep. CBR archives are not readable — a CBR is a different kind of archive and the app is honest about skipping it.

An OPDS catalog

OPDS is the standard catalog language self-hosted library servers speak (Calibre-Web and its relatives, for instance). In Settings › Books, enter the catalog address with a username and password. The whole library becomes browsable from the shelf: folders open into sub-catalogs, and a tap downloads the book, preferring EPUB where the catalog offers a choice. Credentials stay on the device. A catalog that answers with an error page is refused rather than saved to the shelf as a broken book.

The library hub

The hub is a WebDAV share the app uses to move books and reading positions between your own devices. Point every device at the same address and:

• A book added on one device is offered on the others. Books you have not fetched yet show as ghosts; tap a ghost to fetch it.
• Big books wait for Wi-Fi if you say so, and a size ceiling keeps a 300 MB scan from arriving on a phone unasked. A book you tap is wanted and comes anyway; only the Wi-Fi courtesy is kept.
• Uploads are streamed, so a 100 MB audiobook never sits whole in memory, and a half-arrived file is never mistaken for a book.

The hub can be the same WebDAV server that syncs your day pages, on its own folder.

The shelf

Two bands. Read this period follows the almanac strip: what you actually read in the week or month you are looking at. All books is the whole library and stays out of the strip’s reach. Folders move you between shelves; the shelf controls set sort and cover size, and what counts as “continuing”.

Reading

The reader keeps the same quiet footer for books and for feed articles. Select a passage to highlight it, make a note on the selection, pick it onto today’s page, or read it aloud. Fonts, spacing and colorways are shared between books and articles, so setting the reader once sets it everywhere. Read-aloud flows across page ends instead of stopping at each one.

Comics and manga

Comics are books on the same shelf. A comic gets a balloon index when it opens, so you can move balloon to balloon on a small screen, plus a panel walk with its own reading direction. See Comics: balloons and panels.

Web pages as books

From The Net, Save as a book binds a page into an EPUB on a Web shelf, images included. See The Net.