Puzzle Me Twice

From Alex Bellos--puzzle-setter to the Guardian--here are 70 irresistible challenges that have stumped the sharpest minds he knows, even when warned! For example, how many mistakes are there in the following sentence?
This sentence is kurious because it
it only contayns three misteaks.*
Bellos wrangles math and physics, logic and wordplay, optical illusions, card games, and more to tie readers' brains in pleasurable knots. These puzzles are quick to browse and simple to state, but look out: Each one has a right-looking wrong answer to lead you astray.
Suitable for novice and "pro" puzzlers of all ages, Puzzle Me Twice is the perfect diversion for your brainiest friends. Being wrong has never been so much fun!
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* There are five mistakes: Kurious, contayns, and misteaks are misspelled, the word it is repeated, and three is miscounted.