Ladies and Gentleman, Boys and Girls, Children of All Ages... Just as the Quirk family was settling into Normal... Ta da! The circus comes to town! At school, Molly, Penelope, and Finn are all learning circus skills in gym class. At home, they are putting similar skills to good use; it takes fancy footwork and stellar detective work to keep their nosy neighbor from snooping around and uncovering the Quirk family secrets. Each day in their new town makes one thing very clear: Life in Normal is a high-flying adventure!
I don't think you would need to read the first book before embarking on this one. The author is careful to explain characters and ideas carried over from the first book.
Finn is really a delight in this book. He learns about the idea of pranking people and he and grandpa have a few really good belly laughs after they pull off some good pranks. We also get to know the little fairy grandmother in this story a little better. There is a great lesson on not judging people (I.e. Their neighbor, Mrs. DeVille, for example).