Manually Adding Books to iPad via Apple Devices

For storage purposes I like to manually add previously purchased epub files to my iPad 8th Gen IOS 17.3.1

I previously used iTunes to move files from my Windows 11 PC to my iPad

I installed Apple Devices this week and found the process more difficult and can't transfer book files to the iPad using Apple Devices

I have 'Manually manage music, movies and TV shows' ticked but when I drag a epub files from my PC to my iPad in Apple Devices the file shows up under 'Apple Devices' - 'On My Device' -'Books'.

Unfortunately the file doesn't show up under Books on the iPad

In Apple Devices under my iPad I see a folder called Files which shows what apps can transfer documents between the iPad and computer.

I don't see Books in here or any way of adding it?

Any thoughts? Is there an alternative way of manually adding books to an iPad using Apple Devices?

Thanks

Paul