Knock-knock. Who's there? Blippo and Beep! Blippo and Beep are a pair of silly robot friends. While Blippo is good-natured and eager, Beep is a bit more serious and practical. But when they start to share knock-knock jokes with each other, Blippo doesn't really understand how they work, and Beep begins to run out of patience! Exciting, easy-to-read books are the stepping stone a young reader needs to bridge the gap between being a beginner and being fluent.