Here's the solution to the Leap Years exercise in the same chapter:

(everything looks OK to me)

------------------------------------------------------------
puts 'Please enter the starting year'
input = gets.chomp
puts 'Please enter the ending year'
input2 = gets.chomp
puts ''
puts 'The following are leap years:'

input = input.to_i - 1

while input < input2.to_i
	input = input + 1
		if input%4 == 0 || input%400 == 0 && input%100 != 0
			puts input.to_s
		end
end
---------------------------------------------------------

I might continue posting the solutions for the rest of the book if I
decide to keep on reading.

This way I won't develop any bad habits (because hopefully the
solutions will be scrutinized by at least one other person) and it'll
help anyone else reading the book who gets stuck. I doubt the author
of the book will ever get around to publishing the "official"
solutions.