This is book four in the “How to Train Your Dragon” series. It is the next book after “How to Speak Dragonese”.
In this book, Hiccup’s friend Fishleggs comes down with a sickness, which is a nasty case of Vorpentitis (a sickness caused by the sting of a Venomous Vorpent).
Hiccup decides to embark on a crazy adventure to get a so-called non existent vegetable (a potato) from a s0-called non existent land (America) to cure his friend.
I found this book to be the most adventurous book in the series, which I really like.