What about sth./doing sth.你认为...怎么样?是用来征求对方意见的.
what (about) the dictionary?你认为这本词典怎么样?
What is sth.about ...问"...是关于什么的?",如:
What is the text about 这篇课文是关于什么的?
没有What is about sth.的说法.因此不能加is.