Albert Einstein and Relativity for Kids: His Life and Ideas with 21 Activities and Thought Experiments (For Kids series) by Jerome Pohlen http://www.amazon.com/dp/161374028X/ref=cm_sw_r_pi_dp_sp8jub1Y32TM8
These Uncle Albert books are the reason my 5 year old can explain to someone with scientific certainty the relativity theory while playing superhero. Lets just say physics professors are amused by him. Told from the point of view of what is supposed to be Albert Einstein's niece learning about relativity (and other physics concepts) from her uncle and how it applies to everyday life. If telling to elementary kids best to strap on that white wig and tune up the european accents.
Albert Einstein (Giants of Science) by Kathleen Krull. $13.67. Publisher: Viking Juvenile (October 15, 2009). Reading level: Ages 10 and up. Author: Kathleen Krull. 128 pages. Series - Giants of Science