Abacus is a middle-grade novel that whisks readers along with AP, #13; the 12-year-old protagonist and science geek, who travels through #13; time with Kate, his oh-so-bored 15-year-old sister. Their journeys #13; to Arthurian England, the Wild West, and Ancient Egypt get them#13; into some very tight spots, but AP uses his broad knowledge of #13; science to help them escape. And stalking them on every trip is a #13; hooded stranger whose attacks show he'll do anything to stop them. #13; #13; Besides being a fast-paced and engaging novel, the story has #13; some additional features including: #13; ? easy to follow instructions at the back of the book for repeating #13; AP's experiments#13; ? separate supplemental reading lists for kids, parents and educators#13; ? extra notes that delve deeper into the historical times and settings#13;