Books like Captain Underpants and the Wrath of the Wicked Wedgie Woman

Steadily I'm making my through this series. Wrath of the Wicked Wedgie Woman was not nearly as good or as funny as the last four books. I think it's because there wasn't enough conflict? It's hard to put my finger on why this one wasn't as good. I just didn't like the main villain I guess. Her main "weapon" was spray starch. It kind of reminded me of Superman and Kryptonite. Although it makes sense why Captain Underpants wouldn't want his underwear starched, it just didn't seem "enough" for me. I didn't add this tidbit before, but If you haven't read Captain Underpants and you wanted to, you don't have to read them in order. They (George and Harold), do a review of what happened in the last book as a comic book you read within the book. Hopefully you understood that. Looking forward to many more adventures with George and Harold.