The titular T. Rex only puts in a cameo but readers will still be wowed as super-swimmer Phelps recaps the six-year regimen that put him in shape to win a record eight Golds at the last Summer Olympics. He livens his recitation of laps and reps considerably with comparisons—“I trained for six years! That’s a kindergartener’s whole life! That’s the same as 42 dog years!”—and after swimming 17 races in nine days to reach the finals won the 100-Meter Butterfly by 1/100th of a second: “about the length of a fingernail.” In blocky digital paintings Jenkins stacks up pizza boxes, whole sports teams, Washington Monuments and herds of dinosaurs to back up the claims about distances run, calories consumed and weights lifted, and closes with a view of the athlete lounging on a sofa, holding a bowl of broccoli and thinking up new goals. (Perhaps appropriately for the audience but possibly compromising the book’s timeliness, the athlete’s suspension for smoking pot goes without mention.) Motivational and self-aggrandizing, like most of its ilk, but not too heavy-handed with the Message. (Informational picture book. 6-9)