Jeffrey S. Rosenthal, author of the bestseller Struck by Lightning: The Curious World of Probabilities, was born on Friday the thirteenth, a fact that he discovered long after he had become one of the world's pre-eminent statisticians. Had he been living ignorantly and innocently under an unlucky cloud for all those years? Or is thirteen just another number? As a scientist and a man of reason, Rosenthal has long considered the value of luck, good and bad, seeking to measure chance and hope in formulas scratched out on chalkboards. In Knock on Wood, with great humour and irreverence, Rosenthal divines the world of luck, fate and chance, putting his considerable scientific acumen to the test in deducing whether luck is real or the mere stuff of superstition.