Only diehards need apply! These incredibly difficult sudoku are made to challenge even the most expert solver...and strain their brains to bursting. Each puzzle requires upper-level strategies that have been honed to perfection from regular practice. Designed by powerhouse sudoku creator Frank Longo, they'll have dedicated fans tearing their hair out-and loving every moment. This is a bind-up of books 2, 3, and 4 our four-partAbsolutely Nasty sudoku series.