A to Z Mathematicians by Tucker McElroy, Ph.D.(affiliate link)
The Big Book of Brain Games by Ivan Moscovich (affiliate link)
Dr. Math Introduces Geometry by Drexel University and Jessica Wolk-Stanley (affiliate link)
Everything you Need to Ace Math In One Big Fat Notebook by Ouida Newton (affiliate link)
Help Your Kids with Math by Barry Lewis (affiliate link)
Illustrated Maths Dictionary by Judith De Klerk (affiliate link)
Math Puzzles and Brainteasers Grades 6-8 by Terry Stickels (affiliate link)
The Math Book by Clifford A. Pickover (affiliate link)
Math for Real Life by Jim Libby (affiliate link)
Math Genius by Mike Goldsmith (affiliate link)
Math Labs for Kids by Rebecca Rapoport & J.A. Yoder (affiliate link)
Mental Math Kids Can't Resist by Richard Piccirilli (affiliate link)
Wacky Word Problems by Lynette Long (affiliate link)
The Boy Who Reversed Himself by William Sleator (affiliate link)
Carry On, Mr. Bowditch by Jean Lee Lantham (affiliate link)
Arcadia by Tom Stoppard (affiliate link)
The Cat in Numberland by Ivan Ekeland (affiliate link)
The Blind Geometer by Kim Stanley Robinson (affiliate link)
