The Great Book of Riddles: Magnificent Riddles, Puzzles and Brain Teasers ( The I always get to think of different ways on how to solve it and I felt good.
Difficult Riddles For Smart Kids: Difficult Riddles And Brain Teasers Families Funster Crossword Puzzle Book for Adults: Large-Print Easy Puzzles.
Another reason to buy puzzle books is that doing puzzles and solving riddles may improve your brain performance, which is good for elderly.
Entry level++: (Martin Gardner, My Best Mathematical and Logic Puzzles) Harder: (Raymond Smullyan, what is the name of this book?) Double black diamond.