iPhone 8/Plus How to transfer files from the Books app to another device?

[AMSOS]

I have some pdf and ePub files in the Books app on my iPhone.
I was recently trying to transfer them to a friend who also has an iPhone. While bluetooth was switched on I couldn't see the AirDrop button in the share menu.
That's when I also realised that there doesn't seem to be any other way of transferring pdf or ePub files from the Books app to another phone.
Am I missing something here?
Thanks!

 

[now i see it]

Files imprisoned in the Books app can be set free (normally) when clicking the Share icon at the top.
You should see three choices for escape:
AirDrop
Email
Messages.
Make sure that wifi and Bluetooth is ON when attempting AirDrop.
I don't know why you're not seeing an AirDrop option.

In the future, avoid saving files to the Books app. Only Books should really be stored there

 

[AMSOS]

Normally I do follow what you say. But I'll double check when I try to transfer a book.

Actually these are books in either pdf of ePub format. Do you suggest I just save them in Files and use the reader that pops up there to read them?

The Books interface is nice, so I like to read with that.