Yes, curious is what I am too.
I actually want to know more why it happens, than how to stop it.
By the way, I double-checked with the epub I'm reading now. The main body of text is divided in two html files. I opened the second one to see where it starts. Right enough, when I reached that part of the text on my reader, the double loading stopped. I'm waiting to see now at what point it will start again..