And then there are many interesting tricks to approach those 36. For example, the 'fingers' trick for the 9 times table. (Which leads to consideration of why do the digits of a multiple of 9 always add up to a multiple of 9?) Muliplying by 5 is half of multiplying by 10. Multiplying by 4 is doubling twice, etc.
Before you know it, you just have to drill the ones most common to choke on (like 7x7, 7x8).
In any case, don't let a cursory look at Problem 1 decide the nature of the book for you. There's more than meets the eye. I don't know much about Tony Gardiner but the other author, Alexandre Borovik, has a wonderful blog called "Mathematics under the Microscope" (https://micromath.wordpress.com/) (and also a book of that name); to everything he brings a profound perspective with a light touch, a unique combination. A couple of memorable posts I still remember from over a decade ago:
• “Psychophysiology of blackboard teaching” https://micromath.wordpress.com/2010/09/24/psychophysiology-...
• “Achilles, Tortoise and Yessenin-Volpin” https://micromath.wordpress.com/2009/02/16/achilles-tortoise...
• All the posts about "a childhood story".
Anyway, I haven't gone through this book so far, but skimming through some chapters and how they are put together, there is a lot of gold here. See for instance Problem 78, which is simply twenty opportunities to think about "3 - 1 = 2".