Thickness is all subjective, the construction and attention to detail is superb as is the finish, if you like the dimensions that is all that is relevant.
But if you actually want feedback, my opinion is that the sides are around 3 times thicker than looks good for a box of that size and the hinges would be suitable for the current thickness but too substantial for for the overall dimensions.
So a superb box that when shut looks fantastic and truly impressive skill in construction but a bit too Shrek like when open.