iPhone Read ePubs on iPhone 4

I have an iPhone 4, running IOS 7.1.2, the max possible.
I want to test some ePubs for iBooks on it.

It needs the iBooks app to do that, but the iTunes store says only available for iOS 10.

There were iBooks for iOS 4, so how can I get an old version?

I have no other Apple devices, use iTunes on my PC to load stuff on it. So the work around of installing a new version on another device under my name first will not work.

Are there any other apps that I could use?

-- tried MapleRead, that needs iOS 8.