Rating: 

[An example of rolling 2 dices]
r_1 = rand(6); r_2 = rand(6)
r1 = r1>0?r_1:1; r2 = r2>0?r_2:6

And a comment like this:
"...a little fancy footwork to make sure it does not return 0..."

These are signs that you just got duped.

Obviously the author isn't well-versed in Ruby.

No feedback, lots of errors, low on technical.

More importantly, this thin book has a price of a THICK book.