This Lego set is very cute. It has several options to build so once you accomplish one, you can tear it apart and begin again. It has a lot of tiny pieces so I would be cautious about children who still put hands or fingers in their mouths. It was hard for my 4 yr old to get some parts apart. I think 4 is a little too young to play with this set by themselves, but we did have a great time working on it together!
My niece, who will be turning 6 soon, needed something more challenging than the little kid toys I've gotten her in the past. It was very reasonably priced so I felt I could take a chance on it. Also there are enough pieces to challenge her, but not so many that I won't be able to help her figure it out.