This Kakuro book is a difficult one! Have a look at it:
My first Kakuro book contains 200 puzzles. First 150 Kakuro puzzles are standard Kakuros, including some big ones (up to 20×20) and the final 50 puzzles are Kakuro variants, which is something not found in any other Kakuro book!
The second Kakuro book contains 150 Kakuros (Cross Sums), but it also contains 50 KENKURO puzzles, which should also be called Cross Sums+Cross Products+Cross Divisions+Cross Subtractions. 🙂
This second collection of Kakuro puzzles is also available as a Kakuro game on Kindle!
Speaking of Kakuro games on Kindle, there is also an introductory game of Kakuro for Kindle, with somewhat easier puzzles: