Throne of Fire is the second book in the Kane Chronicles by Rick Riordan. These books follow Carter and Sadie who are Egyptian Magicians. In this book they must find three scrolls and rescue the God Ra who has been trapped so they can save the world from Aphohis who plans on swallowing the sun and destroying the world. The two face many trials and battles throughout the book and they met many different Egyptian Gods who helped them along the way.
I have mixed feelings on this book and the series. I've loved the Percy Jackson books and my daughter has listened to all of those books (plus The Lost Hero) multiple times. When I gave my daughter the audio book for The Red Pyramid she listened to it a couple days and then switched back to Percy Jackson because she was bored (granted she's seven and much younger than the intended audience).
The mythology in these books is far more complex and confusing than the greek mythology of Riordans other series. The sheer numbers of Egyptian gods and similarities in their names (Anubis is a cute helpful god Aphosis however wants to swallow the sun, Bast is the cat goddess while Bes is the god of dwarves who scares people with his speedo) make it difficult to sort everything out.
There were times when I loved this book and there were times when I thought it was never going to end. The dual point of views seemed to make the book seem even longer and the book was very long period. I think if the story had been more streamlined I would have enjoyed it more. If you enjoyed the first book then you will like this one, it's much like the first and you'll like it. However if you were frustrated by the first book and were hoping that this book got better I'd skip this one. It has all the problems of the first book plus a few additional ones. There are far too many characters and too many deviations from the main plot.
Appropriateness: There is some romance in this book. Both siblings find love interests and Sadie has a love triangle to deal with. This series requires a more mature reader than Riordan's other series. The plot and mythology is far more difficult to understand than the Percy Jackson series. The lexile for the first in the series is 650 putting it about a fourth grade level but the plot is far more advanced than the vocabulary level (and this shows the downfall of grade levels that are calculated by computer). This is not a book that I would hand to an elementary school aged child (unless they were advanced) because of the complexity and disagree with the recommendation on most sites as it being written for 9-11 year olds (remember my daughter who is reading and listening on that level was bored by this series). This book is one that middle schoolers would enjoy and even find a little challenging. I would recommend this book to 11-14 year olds (and it's great for boys).