So far I've solved #s 1, 5, and 7. I consider myself advance. I can do 9X9 and I try not to use hints when solving, even with 9s, and depending on the puzzle I can keep the numbers straight without hints. I've been playing KenKen for about two years now. This book is going to last a while. Just know going in that it's going to be HARD. They meant the Ferocious part. This is going to be challenging even for advanced players.