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?

After four days in a row of indoor recess, Miss Mackle's students are bored-until Harry decides to solve the biggest mystery ever in Room 3B! There's a locked closet in the classroom that's been sealed off for years, and he wants to know what's inside. So Harry drafts Doug, Song Lee, and the rest of the class to help him investigate. Their search reveals many surprises-from a hidden trapdoor to...eyeballs! What secret treasures does the closet hold? Is it something more horrible than even Harry can imagine?

When Harry comes to school wearing a necklace, the whole class is intrigued. Harry opens the necklace and reveals a mini-microscope&150perfect for looking at the mold experiment Room 3B is working on! Everyone wants to try it, so Harry promises to show them a kingdom of mushrooms at recess. But there is one catch. They will have to go outside the playground fence, which means breaking a school rule. If they follow Harry, will they ever be able to face Miss Mackle again?

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?

"When his best friend Doug discovers his top-secret hideout, Harry enlists his friends' help to save it from being developed into an apartment building"--

When Harry finds an ad in the paper for a used telescope, Miss Mackle suggests that the class raise money to buy it. The telescope will make their moon study unit even more exciting! Once they get the telescope, the class can have a nighttime moonwatch. But Harry wants to do more than watch the moon-he wants to go there! Can Harry really take a trip into outer space? "There's laughs aplenty in the short snappy text-just the thing to turn new readers on to books." (Booklist)

Third grade brings lots of surprises, but one thing hasn't changed a bit--Harry and Sidney are still sworn enemies. And their relationship only gets worse when Sidney accidentally kills Harry's pet spider. But Harry comes up with a horribly funny way to get revenge during a class trip to a creepy copper mine.

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?

The kids in room 3B have found out that their teacher, Miss Mackle, is engaged! But who is the lucky groom? Leave it to Harry and his best friend, Doug, to find out. Harry goes into detective mode, and wastes no time starting his investigation. Doug is willing to help?until he sees Harry stealing a piece of evidence. Doug can?t believe it! But Harry thinks his risky move is worth it. After all, he manages to crack the case and tells everyone who Miss Mackle is going to marry. But does Harry really have all the facts, or has he made a horrible mistake?