Hey, As for exercises I feel they focus heavily on math with numbers, Collatz problem.Maybe there could be more exercises with only a small change and some that tell a story e.g favorite pizza (with a seq of ingredients), 99 bottles of beer, animals, etc. I feel also that text is very short and only scratches the surface of each topics. I understand that it may be intentional, but it ends so quickly ;-)
I find the code listings with explanations with numbers very useful, and personally think that these should be even more. If you would like to expand this text in the future a good idea in my opinion would be to add chapter about basics of TDD, and how beginners could write tests to test their knowledge - either with asserts or unittest library(I did't use testament - maybe it would be better).