I remember loving these as a kid but I haven't done one since then. Funnily enough staying in the lines and complex neurological conditions don't go hand in hand.
I got about 2 minutes in and got annoyed with it because:
1. The brush is too big to paint the tiny shapes
2. The paint isn't thick enough to hide the numbers
3. Hand tremor
So I said f---it to giving up on a painting by numbers instead.