I can't write a meaningful review without discussing some high-level things about this book, which I consider to be kind of spoiler-y, so I'm just warning readers up front, in case you'd rather not read them before you read the book.
In the first book, our protagonist, Petra, is very spirited, while in this book she is sort of a full-blown brat, to be honest. After a while I got tired of her being so oppositional all the time. Even when I could somewhat understand why she was being less than compliant, to be honest, it got old for me.
On the other hand, I really liked the Tomik/Neel story, especially, of course, the parts related to language. And naturally Agatha's ability is one I wish I could take advantage of!
I thought the overall story was really compelling, and I liked the premise and how things ended up (with the exception of what may or may not have happened to Petra's father, of course). The bonus of encountering real people from this time period was a lot of fun.
One note, my emotions are all over the place these last few days, so when it seemed like Astrophil was lost, I almost started bawling - luckily that was resolved quickly. I would love to have an Astrophil of my own! He's a real favorite for me.
I'd be remiss if I didn't mention the books' neat covers, by David Frankland. They are full of cool detail and really draw the reader in to the story.
All in all I'm really looking forward to reading the third book in this series. Recommended.