The Wyverns' Treasure: Nathaniel Fludd, Beastologist Book 3 by R. L. LaFevers
After tangling with the deadly basilisk, Nathaniel Fludd is glad to return to England with his Aunt Phil. But someone has ransacked their home, and their best suspect is the sinister man who's been trying to steal the Book of Beasts.
Before Nate and Aunt Phil can find the culprit, they are called to Welsh countryside. The wyverns (giant dragons) are in an uproar. Could the same man who ransacked the Fludd house be behind the rift with the wyverns? And just what does he want with The Book of Beasts? But before Nate can solve that mystery, he must calm the dragons before it's too late. It's just another day at work for the world's youngest beastologist!