I've got it. I do try to use it on a daily basis but don't always find the time, so it's more like every other day. I mostly use it at night and my brain age is around 33 or 34 (I'm 33 so pretty chuffed with that score!).
Saying that, I used it one lunchtime when I was feeling bright 'n breezy and got a score of 21!!
I do love puzzle books though so my brain is quite well trained in a lot of respects. I'm useless at the calculations though. What's 8 x 9 again? :oD