My book tells me "partial shade". My Pieris only gets early morning sun and is doing fine in a large pot. It's about 4 yrs old and looks beautiful right now. My mother has 2 in her garden in clay soil under trees, also doing very well. I expect someone will say they have one doing well in sun. Plants often grow against the 'rules'. Mine is in ericaceous compost which I believe is recommended.

I agree with Seabird about the ericaceous compost. I have "Forest Flame" in a pot but mine is against a south facing wall and gets sun from dawn until about 4pm!

All the books state partial shade but thankfully plants can't read! If you have the choice go for part shade.