No wonder it’s America’s number one pastime--researchers have found that doing crossword puzzles will improve your memory when you’re older, and, if you’re a kid, improve your vocabulary and better your chances of getting into the best colleges. What makes this collection special? The answers are fairly common words and phrases, but the clues are diabolically difficult. They’re full of mischievous misdirections, trivia, puns, and other trickery. Try these clues: “Star witness” (ten letters), “Change of heart” (fifteen letters), 2001 Hollywood Walk of Fame star recipient (eight letters). Answers: ASTRONOMER, ORGAN TRANSPLANT, DEAR ABBY. Warning: the last 10 are the hardest of all.