Yomu for iOS allows you to import ebooks from a variety of different sources.

You can download documents directly from your browser or import files with Apple’s Files App, AirDrop, Drag and Drop, iTunes File Sharing, Dropbox, Google Drive, OPDS or any other third-party storage provider.

In order to import an ebook from a website, tap on the corresponding download link and choose “Open in Yomu”. To import documents from a storage provider, go to the library, tap the plus + icon on top right and select a service.

With Yomu for Mac it is even easier to import books. Simply drag and drop files to your library or open documents by clicking the add button (+) on top right.

You can either add individual documents or use batch import for several at once. Batch import is limited to maximum 100 files, because with more your device could run out of memory and iCloud has troubles syncing large amounts of data. To add more books, you would need to split your collection into multiple batches.

Yomu is intended as simple ebook reader, not a document management system or server. It is recommended to still keep your original books on your computer, some kind of cloud storage provider (iCloud Drive, Dropbox, Google Drive, …) or to use a dedicated ebook management software like calibre.

The app is optimized for up to 500 books or a total size of 600MB. Everything above these limits can lead to memory or storage issues and synchronization no longer works reliable.

Any import creates a copy of the document and saves it for offline access. When importing a document, the corresponding format is parsed and validated. In case an ebook does not conform to official standards, a warning is displayed.

This usually means that meta information (title, author, table of contents, …) will be missing. In most cases, the contents of the ebook still can be displayed, but there is no guarantee it will render correctly.

Yomu for iOS directly supports the following storage providers:
– Dropbox

You will need to authenticate using your login credentials and grant Yomu access to your files. Afterwards, ebooks can be imported by browsing to the corresponding folder. You can directly select individual documents or load all files in a folder. To switch to batch import, tap the top right batch button (4 bars) and select any or all files to download.

Access to a provider can be disabled in the settings, or you can remove Yomu from the linked apps in the corresponding provider’s account settings.

Other cloud storage providers like Google Drive, Microsoft OneDrive or Nextcloud can be integrated via Apple’s Files app as described below.

Apple’s Files app is directly integrated for iPhone and iPad devices.

Create a folder on iCloud Drive and add your books. Launch Yomu and go to Import (+) > Files to open the Files App extension. Navigate to a folder and select the files you want to import to your library.

Other storage providers such as Dropbox, Google Drive, OneDrive, Nextcloud or Owncloud can also be connected in case they offer an iCloud Drive integration.

After you install and enable the corresponding integration with Apple’s Files app, they should be listed under Locations in the Browse sidebar.

1. Download and set up the third-party app
2. Open the Files app, tap the Browse tab
3. Tap the More button (…), then tap Edit
4. Turn on the third-party app
5. Navigate to Locations to access it

Apple Support references:
Files app documentation
Use third-party cloud apps in the Files app

You can also import your books from a server or network-attached storage (e.g. Synology NAS). After you connect to a server via Apple’s Files app, you should be able to access it under Locations or Shared like any other storage provider.

Refer to this TechRepublic article on how to set it up:
How to use the Files app to connect to a network server from your iPhone or iPad

Documents can be transferred with iTunes File Sharing to the Yomu iOS app.

Connect a device to your computer and open iTunes or the Finder app on Mac Catalina. Navigate to the attached device and open the Files tab where the Yomu app will be listed. Add or simply drop your ebooks to the Yomu section.

All added documents will be transferred to the app and are available in Import (+) > Documents. Select a document to import it to your library. Or you can switch to batch import (top right button) to load multiple files at once.

With OS X Yosemite, you can also simply AirDrop an ebook directly from your computer to your iPhone or iPad.

Enable AirDrop, then drag a document from your computer’s finder to the corresponding device. Select Open with Yomu to import the transferred ebook.

Another option for iPad devices is to import books by drag and drop.

Open Apple’s Files App as a slide over or in split view. Select iCloud Drive and navigate to a folder containing books. Tap and hold a document, it will expand slightly, ready to follow your finger around the screen. Drag the file over to Yomu and drop it on the library to import the book. You can also select multiple files at once and drop them to batch import.

Open Publication Distribution System feeds let you directly access Calibre or other book catalogs on your iPhone, iPad and Mac.

To open a catalog, first tap edit to add a new server. Enter a name and valid feed url. With Universal Clipboard enabled, you can also copy the url from your desktop browser and paste it on a nearby device. If your server uses basic or digest authentication, fill in the optional login user and password.

Your device must be allowed to access the feed url. You may have to grant the required Local Network Permission to connect to your OPDS servers.

Yomu for Mac lets you add books by drag & drop or open documents.

Open Finder on Mac and navigate to a folder containing ebooks. Simply drag files in EPub, Mobi, Kindle, Comic or PDF format to your library. A green plus sign will appear and you can drop the dragged files to import them.

As an alternative, you can also directly open documents. Click on the add button (+) to open supported files, use command or shift click to select multiple. A preview of the selected ebooks is displayed, click on Import to add them to your library.