This is another two books in one book, which I like because of the cost effectiveness of it. Attack of the Robot was a good, action packed story that kept my nephew entertained and interested. We especially enjoyed the ending of the story.
Heroes United was a little slower paced, and was really more of an introduction to each of the main Super Friends (Superman, Batman, Aquaman, Flash, and Green Lantern) and their super powers. This didn't hold my nephew's attention quite as well as Attack of the Robot, probably because he already knows who these heroes are and what they can do. Still, it's a fine read for the age group for which it's intended.