[AlexBell]

Thanks for the responses, and the trouble taken to try to help me. But I'm afraid I only understand about one word in three of the suggestions.

I do have a wifi connection - that's how I transfer ebooks from Dropbox to Bluefire on my iPad - at the moment that's my favourite ereader on the iPad.

Could you give me a name for 'one of the thousands of file managers...' Should it go on my Windows 7 computer or on the iPad?

Last night I stumbled blindly around the iPad while it was connected to iTunes and my Windows 7 computer. I found a way to display the book related apps with which I could transfer files to the iPad, and found that iBooks was not amongst them. I don't know whether iBooks would have appeared on that list before the iOS 8.4 'upgrade', but I do know that I could transfer my ebooks to iBooks by dragging and dropping. And I can't now.