That's similar in art style to the current line of books from series and movies, especially the first one. The Frozen one looks similar to the first one there and I think we can all agree that Frozen isn't drawn in that style itself.

The illustrator of the first one, Mike Wall, has a blog with the other titles he's done for Disney Junior. http://mikewallillustration.blogspot.com/

I'm not sure about the second one. There's not an illustrator on the front, so it's hard to say. I think it's more of a stylized version of the show.