Bought it for the challenge, and it definately is, however it does not have the tight fit that I expected of the pieces. In many cases it's difficult to tell if you've got the right piece or one that's close. Other than that, it provided several hours of fun, but I highly recommend having a pair of tweezers handy. Because of the loose fit, putting in or pulling out a piece (Or test fitting a piece) can result in massive damage when trying to use your fingers.
This was a pretty fun little puzzle. It took about 2 hours to put together. The quality is not great, so the pieces don't fit snugly together. Recommend having tweezers on hand because it's hard to position the pieces without disturbing the rest of the puzzle.