I just received this and can't wait to read it to my boys (ages 4.5 and 6). They are a bit timid and can have nightmares if they see anything too scary. But, being typical boys, they love the super heroes. This will be a perfect intro to the villains without being too scary or introducing too many concepts they can't understand. I really like how the villains are introduced in the context of the Lego sets (many of which we have). The only part that they would ask umpteen questions about is the page that references Harley Quinn in an asylum with the Joker (how do you explain an asylum to a 6 year old?) But I'll change a couple of the words (hospital instead of asylum), and it will be fine. My boys are going to love this!