The difficulty level soars, as even more tricks get added to the mix: X-Wing; Swordfish; XY-Wing; XYZ-Wing; and the Gordonian Rectangle.

Top solvers can try their hand at the One-Sided Gordonian Rectangle; Extended Gordonian Rectangle; Gordonian Polygon; and Alternating Digits. (But they can take comfort in knowing that no more than one will occur in any single puzzle.)

If you're going to be sitting in one place for a while, a tricky sudoku is just the thing to pass the time. (Make sure you've got a spare eraser under the sink.)

The logical choice for lavatory reading. Easy sudoku are perfect for solving when you have a few minutes on your hands...wherever you may be. Just toss this pocket-size book into your bag or leave it in a convenient location, and you'll be ready for sudoku-solving enjoyment at any moment!

If you want easy sudoku that's also easy to take on the go, Sit & Solve No-Sweat Sudoku is right up your alley. Sudoku sensei Frank Longo has crafted 60 gentle logical conundrums, none of which require upper-level solving techniques to conquer. Grab a pencil and give your brain a stretch with Sit & Solve No-Sweat Sudoku.

Sudoku super-master Frank Longo and mental_floss, the magazine for trivia lovers, bring fans a collection of superb puzzles sure to stimulate the brain. Longo's puzzles are always top-notch, and because these increase in difficulty as the book goes along, they're perfect for helping solvers build their skills.