Manually adding books to Nook App on iPad I need to &quot;side load&quot; a number of eBooks (mostly epub and PDF) into the Nook App on my iPad and iPhone.  This is something I am able to do with my dedicated Nook eReader like the Nook HD or the Glowlight (not the Samsung tablets). To add books, you simply connected it with a USB cable which then made the Nook look like a USB storage device to the Mac (or Windows machine) and you simply copied the files over.
For the record, I use Calibre to manage my personal library and to handle the file syncing to the Nook device.  As long as the device appeared as USB storage, it would handle (copy) it.

...calibre can directly connect to all the major (and most of the minor) e-book reading devices, smarthphones, tablets, etc. In addition, using the Connect to folder function you can use it with any e-book reader that exports itself as a USB disk.

 Source:  Calibre FAQ
This isn't possible on an iOS device as it doesn't show up as a USB storage device.  How can I manually add my personal eBooks to my Nook App on my iPad, iPod, and/or iPhone?
The Nook App isn't very intuitive when it comes to telling you how to sideload books onto your iOS device, however it is possible.  Unfortunately, it's not as simple as just hooking up the device via USB and letting Calibre handle it.  There are two methods:

Via USB (cable) and iTunes
Downloaded from shared site

USB Cable &amp; iTunes
It's fairly easy to drag and drop via iTunes.

Connect your iOS device
Under File Sharing
Drag and drop your eBooks to the Nook folder


Downloaded onto iOS device
This requires the Files App from Apple to access the folders on the iOS device

Download the eBook using your browser (Firefox shown here)
Go into the Downloads directory
Long press the file to bring up the context menu and select Move
Select the Nook directory
Press Move