I read What Katy Did and I enjoyed it. But my favourite book in the series is What Katy Did at School.
It's about Katy and Clover going to a boarding school and get into some funny adventures, eg: the S.S.U.C!
My favourite character is Rose Red (Rosamond Redding) a cheeky schoolard. She sends messages to Katy through their wall because they share a drawer and I think that's great fun. There's also Lilly Page who nobody really likes but I think the book wouldn't be so good without her. I don't like her parents though, Mr and Mrs Page (Cousin Olivia).
The only problem is the Kindle Version but it doesn't bother me. There are just some occasional spelling errors and Mrs and Mr starting a new paragraph...
A must-read to a Katy Fan.