The most obvious improvement I saw from the first book was that this time, the plot moved really well. Things were happening! And it was a lot better!

In addition, except for one (I think) part where they switched personalities again, Tilly and Oskar's characters were much easier to pin down. Which led to an incredibly interesting character arc for Tilly, one that has a lot of potential for future books, and I'm very excited to see where it goes.