Blog · 21 October 2026 · 5 min read
The best ebook reader apps for iPhone Duo
Which ebook readers fill the iPhone Duo's 7.6-inch inner display, which show two facing pages, and which still run in a small window, checked two days before launch.
Open an iPhone Duo and you have a 7.6-inch screen with a fold down the middle. That is close to the shape of an open paperback, so reading on it is an obvious idea. Whether that works well depends on the app: some fill the screen and lay a page each side of the fold, others still run in an iPhone-sized window with empty bars around it.
This guide was written on 21 October 2026, two days before the iPhone Duo goes on sale. Apps will change once people have the phone in their hands, so treat each status below as a snapshot and check the app's "What's New" before you buy anything.
A note before we start: we make Glosa, one of the apps below, and this blog is ours. Glosa is not on the App Store yet. We have tried to describe every app, ours included, by what it does today.
Why some apps look small on the iPhone Duo
Apple's developer talk on the iPhone Duo describes three cases. An app built with the iOS 26 tools or older keeps an ordinary iPhone size on the inner display, centred with empty space around it. An app built with the iOS 27 tools fills most of the screen but stops short of the status bar, which runs down the right edge. Only an app built with the iOS 27.1 tools goes all the way to the edges.
None of that gives you two pages by itself. An app that fills the screen still has to decide what to do with the fold: stretch one wide page across it, or set one page each side like a book. That second choice is what makes the Duo feel like reading, and so far few apps make it.
Apple Books
Apple Books comes with the phone and is updated with iOS, so it fits the inner display from day one. CNN's review of the iPhone Duo, published on 21 October, says Books shows a page either side of the fold when the phone is partly folded, like a real book. Apple has not documented this yet, and that review is the only one we found that describes it.
It reads EPUB and PDF and syncs your books, places and highlights over iCloud. Best for you if you buy from Apple's store or read a handful of DRM-free books and want nothing to set up.
Kindle
The Kindle app had not been updated for the iPhone Duo when we checked. Version 7.69, released on 9 October, runs in the small centred window, and CNN's review names it among the apps that have not caught up. Your Kindle library opens and reads as on any iPhone, just smaller than the screen allows. We cover this in more detail in Kindle on iPhone Duo.
Best for you if your books are in Amazon's store and you can wait for an update.
Other readers worth watching
BookFusion has release notes that show it was tried on the device: version 1.44.1 fixed a display glitch on iPhone Duo. Whether it shows two pages is not stated. Yomu added iOS 27 support in September, before the iOS 27.1 tools were final, so it probably fills most of the screen rather than all of it. Readest already has a two-page mode on wide screens, but nothing says yet that it turns on for the Duo.
Kobo Books, Google Play Books and Libby all shipped updates in October, and none of their notes mention the Duo. PocketBook Reader and KyBook 3 have not been updated since the iOS 27.1 tools appeared, so they most likely run in the small window.
Glosa
Glosa is our reader for iPhone, iPad and iPhone Duo. It is built with the iOS 27.1 tools, so on the inner display it reaches the edges, and it treats the fold as the spine of a book. A paged EPUB is set as two pages, one each side of the fold, whether the phone lies flat or stands half folded, and you turn both at once. The library splits into two halves the same way, and the bars and buttons stay off the fold. On the 5.4-inch outer display, Glosa looks and works as on any iPhone.
Glosa can also translate an EPUB, with Apple Translation on the device (iOS 18 or later). On the open Duo it shows the translation as facing pages: the original on the left, the same paragraphs in your language on the right, turning together. On a phone the translation sits under each paragraph instead.
The rest is the same Glosa as on any iPhone. It opens EPUB, PDF, DRM-free MOBI and AZW3, TXT, Markdown and HTML, and imports from Files, whole folders or OPDS catalogs such as Calibre. Double-tap a word and you get its meaning in that sentence, in any of sixteen languages. It reads aloud with Apple voices or downloadable natural voices, and syncs through your own iCloud with no account to make.
What it lacks: it is not on the App Store yet, a PDF still shows one page at a time on the Duo, and it cannot play audiobooks. It is free, with no ads and no in-app purchases; AI meanings have a free daily allowance. Best for you if you want the Duo to read like a book, or you read in a second language.
Side by side
| App | On the open inner display (21 October) | Two facing pages | Price |
|---|---|---|---|
| Apple Books | Fills the screen | Yes, per one review, when partly folded | Free |
| Kindle | Small centred window | No | Free |
| BookFusion | Updated for the Duo | Not stated | Free, plans from $1.99 a month |
| Yomu | iOS 27 support, likely most of the screen | Not stated | Free, Pro $7.99 |
| Readest | No Duo update yet | Has a spread mode, not confirmed on the Duo | Free, plans from $4.99 |
| Glosa | Edge to edge | Yes, for EPUB, flat or half folded | Free, not on the App Store yet |
Which one to choose
If you read Apple's books, start with Apple Books; it is already there and seems to do two pages. If your library is on Kindle, it still works, in a smaller window, until Amazon ships an update. If you want facing pages for your own EPUB files, translated books side by side, or word meanings without leaving the page, that is what Glosa is built for, and it will be free when it reaches the App Store. For more choices on any iPhone, see The best EPUB reader apps for iPhone and iPad.