The line is
My question is about the usage of why is いう used in this relative clause and not another form.
俺は持っていた本を机の上に置いた-I placed the book I was holding on the desk
彼女を横になったまま見上げつつ- This says he does the above while lying down and looking up at her.
呆れたように言う- This modifies her but the question is how. Does this sentence narrate himself as doing all this as she speaks(if so, why る-form), or what else could it mean?