The "Who Would Win?" book series is a popular children's nonfiction series written by Jerry Pallotta and illustrated by Rob Bolster. The books feature two different animals facing off in hypothetical battles, comparing their size, strength, speed, and other abilities to determine which animal would win in a fight. The series is designed to teach kids about animal anatomy, behavior, and interesting facts, using photos, charts, and illustrations to engage young readers

. The series includes many titles covering a wide range of animals such as reptiles, mammals, sea creatures, dinosaurs, and insects. Examples of matchups include Lion vs. Tiger, Hammerhead vs. Bull Shark, Polar Bear vs. Grizzly Bear, and Triceratops vs. Spinosaurus

. There are multiple collections and box sets available, such as the "Ultimate Rumble Collection" with eight books featuring over 100 animals, and other 10-book box sets with various animal battles

. Overall, the "Who Would Win?" books combine education with fun by letting kids predict the outcomes of animal battles while learning about the natural world