I have found a lot of Kakuro books that are just not that challenging, or books that have 125 easy puzzles and 25 hard ones. I like that this series provides a consistent gradually increasing challenge.

I really enjoy kakuro and I love being challenged. The puzzles increase in difficulty so you never get bored. I am up to puzzle 110 and have not lost interest at all; I'm really enjoying it.

I love this series. The last two books, Brown and Black Belt are more challenging.

This is an excellent book for those of you who have mastered Kakuro and want a little challenge, without having to think too hard. These puzzles can be solved without guessing or very much notes. If you want a really good challenge, go for the Black Belt Kakuro puzzles.