BookShelves reads 12 file formats across ebooks and comic books. Some are opened directly; others are converted to EPUB behind the scenes during import. The result is the same either way — the book appears in your library ready to read.
For step-by-step instructions on getting files into the app, see How to Import Books.
Ebook formats
| Format | Extensions | How it works |
|---|---|---|
| EPUB | .epub | Opened directly. The most widely used ebook format. |
.pdf | Opened directly. Supports spread (2-up) mode on larger screens. | |
| KEPUB | .kepub.epub | Opened directly. Kobo’s extended EPUB format. |
| FB2 | .fb2, .fb2.zip | Converted to EPUB on import. Russian-origin format common in Eastern Europe. |
| MOBI | .mobi, .prc | Converted to EPUB on import. Legacy Kindle format. |
| AZW / AZW3 / KF8 | .azw, .azw3 | Converted to EPUB on import. Newer Kindle formats. |
A note on conversion
When BookShelves converts a file (MOBI, AZW, FB2), the conversion happens once, during import. After that the book behaves exactly like any other EPUB — same reader, same features, same performance. The original file is not modified.
Comic book formats
| Format | Extensions | How it works |
|---|---|---|
| CBZ | .cbz | Opened directly. ZIP-compressed comic archive. |
| CBR | .cbr | Opened directly. RAR-compressed comic archive. |
| CB7 | .cb7 | Opened directly. 7z-compressed comic archive. |
Comic books are displayed in the dedicated comic reader, which supports single-page and spread layouts, and right-to-left reading order for manga.
What BookShelves cannot open
DRM-protected files. If a book is locked with copy protection (Apple FairPlay, Adobe DRM, etc.), BookShelves will let you know and skip the file. This applies regardless of format — a DRM-free MOBI will import fine, but a DRM-locked EPUB will not.
DJVU, LIT, DOC/DOCX. These are not ebook formats that BookShelves handles. Converting to EPUB or PDF with Calibre first is the simplest path.
Importing a Calibre library with mixed formats
If you manage your collection in Calibre and have multiple formats per book (say EPUB + MOBI + PDF), BookShelves picks the best one automatically when you import the library folder. The priority order:
Books: EPUB > FB2 > MOBI/PRC/AZW/AZW3/KF8/KEPUB > PDF Comics: CBZ > CBR > CB7 > PDF
You get one library entry per book, using whichever format will give the best reading experience.
Still have questions?
If you have a file that won’t open or you’re unsure whether a format is supported, let us know on the feedback page — include the file extension and we’ll take a look.