When Horrible Harry's pet cat, Googer, sneaks a ride and gets into the school building, third-graders Harry and Doug have to catch him before anyone else does, which means going into some forbidden places.

It’s a horrible day for Harry: a classmate is calling him names; his library book is overdue; he’s last in line for a turn to be the Room 3B VIP. Worst of all, it’s cold and icy outside again, which means no outdoor recess. It’s all too much for Harry—he starts to go cuckoo! Fortunately, there is a solution to Harry’s problems . . . but it comes from a very unexpected source.

Another fun mystery starring Horrible Harry, and this time he's calling the shots! Harry has always loved solving mysteries, and now his friends in Room 3B have learned to love it, too. So Harry challenges them to figure out what he has hidden in his giant, old suitcase. Led by a very determined Mary, the kids take turns solving clues and piecing the mystery together. Their hunt leads them from the classroom to the library, and even to Harry's grandfather's nursing home. Will they be able to solve Harry's mystery? Or will things go horribly wrong for the novice detectives?

Horrible Harry has always loved insects, especially digging in the dirt for them. And, recently, he's discovered a new favorite: earwigs! But when he tries to tell his friends about these critters, only Song Lee listens. So when Miss Mackle assigns groups in Room 3B to act out different fairy tales, Harry sees an opportunity to teach the class about his favorite bug. Will they think his play is hilarious...or horrible?

Harry loves gym class-except for climbing rope. He's just too afraid of heights. But then a special valentine that Song Lee made for Harry goes missing. Now Harry must climb the rope in order to prove who took the valentine. But will he be able to overcome his fear? Or will Harry's Valentine's Day end horribly?

A secret teacher party is happening in the library, but who is the party for? Harry and Doug plan to find out, but when they discover Harry's pet cat, Googer, skulking around their classroom, they have to catch him before anyone else does! They chase The Goog all over school—even into places students (and cats) aren't allowed. Will the boys capture The Goog without being caught themselves? Or will Harry's cat get him into the most horrible trouble ever?

The holiday season is here, and the kids in Room 3B are learning about all the different ways people celebrate. In addition to Christmas and Hanukkah, there's Kwanzaa, Three Kings Day, Korean New Year, and more. All the talk about holidays has everyone feeling festive. Everyone, that is, except Harry. He doesn't seem to care about the holidays, the class pet, or even the new student in class. It's clear that something is bugging Harry—but what could it be?

With Valentine's Day right around the corner, Harry hatches one of his bright ideas. He's going to stage a wedding—to Song Lee!

Doug discovers that though being Harry's best friend in Miss Mackle's second grade class isn't always easy, as Harry likes to do horrible things, it is often a lot of fun.

Recounts the events of a day when everything goes wrong for Alexander. Suggested level: junior, primary.