Even if you're feeling sharp as a tack, you'll enjoy challenging yourself with these engaging brainteasers. And for those of us whose mental faculties are not quite what they used to be, these exercises, which are designed to trigger neurogenesis and rejuvenate brain functioning, could really help! Organized by level of difficulty - from Warm-Up (How many federal holidays can you name in thirty seconds?) to Merciless (Name four-syllable words beginning with each letter of the alphabet), the hundreds of games found in these illuminating volumes focus on enhancing six key areas of cognitive functioning: long-term memory, working memory, executive functioning, attention to detail, multitasking, and processing speed. See 399 Games, Puzzles, and Trivia Challenges here.