This is book five in the Septimus Heap series. Here you can read about book four.
After Beetle, Jenna, Snorri and Septimus returned from back in time, they were met by Jenna’s father Milo, who offers to give them a ride back to the castle. When Septimus remembers that his dragon Spitfyre is nearby on a beach, he decides to ride him instead. Jenna and Beetle also decide to also go along with Septimus.
While riding the dragon, a big storm passes them and lightening strikes Spitfyre’s tail, forcing them to land on the Islas of Syren. At first glance, it looks like a paradise, but they soon realize they are in a dangerous place.
I thought this was a great book. A lot of people think this is one of Sage’s best books. I like all of her books a lot, but this was definitely one of my favourite.