Sudoku U: PhD in Sudoku

We’ll school you in sudoku! Find your grade, improve your play—and graduate to the next level. Sudoku professor Frank Longo has crafted five books with 300 sudoku each, which will take students from solving basics to super-hard, super-expert strategies. Try them and see how far you can go! Warning: these excruciatingly hard puzzles are for sudoku experts only! In order to solve these brain-busting conundrums, you must master not only one upper-level technique, but an array of skills. Every one is a challenge.