Gr 4-6 In this second installment in Yang and Holmes's graphic novel series, which takes place right after the first one ended, the coding gets serious. Students Eni and Hopper and the tag-along comic relief Josh expand their skills as they are tutored by Mr. Bee in his coding classroom and laboratory deep under the school. Mr. Bee reveals to them the history of his fall from grace and his former coding school and drops hints that he knew Hopper's father. The characters are diverse, and this volume begins to touch more on their family lives. The rugby team, hired by the evil principal to find Mr. Bee's most powerful robot turtle, provides most of the villainous action. The narrative is spread a little thin, but the clearly articulated coding lessons are integrated into the plot through the emotional connections among the characters. The children are learning to code with the language Logo, with clever allusions to Logo's history. The black, white, and green drawings are simple and dynamic, with slapstick humor and cleverly depicted coding problems. VERDICT This sequel and the first book are essential for any graphic novel collection and libraries where kids are interested in coding. Lisa Nowlain, Darien Library, CT

Yang and Holmes left Eni, Hopper, and Josh on the verge of a new puzzle at the end of Secret Coders (2015), and this sequel picks up right where the first volume left off. The trio are trying to program a robot, Turtle, to perform a series of actions that will unlock a secret door. There are lots of hidden things at their new school, and the janitor, Mr. Bee, holds the answers to many of their questions, but untimely interruptions get in the way of every reveal, so the kids are left to investigate on their own. Each time the kids write a new program, Holmes breaks down the steps visually, demonstrating each direction with a handy illustration, all in his blocky, expressive, green-hued style. Occasionally Hopper's voiceover invites readers to put the concepts to work by coming up with their own program, before revealing the kids' solution on the next page. Another cliff-hanger points toward even more secrets to come. Well-rounded, informative, and gamelike, this will appeal to plenty of graphic-novel fans.