The continuing adventures of Danny Dragonbreath and his friends. Trivial spoilers ahead.
Namely, that Christiana has gotten a grip on both Danny's being a dragon, and the bus system. After Danny wakes up very, very, very cold, and Wendell and Christiana visit, Wendell suggests calling his great-grandfather. And it's off to Mythical Japan, where his condition is diagnosed -- his fire went out -- and a cure is prescribed -- phoenix eggshell. Thing is, the phoenix lives in the Farthest North, anywhere else being too warm, and prone to being burned by their fire.
The result involves herbal teas, iceworms, hand sanitizer, the grandiloquent names that phoenixes bear, a sign warning of no lifeguard and another forbidding fishing, Wendell's recounting how much he's hated some of their adventures, something that smells of cinnamon, and more.
As with the earlier ones, mixed graphic novel/text. The illustrations do have plot significant events.
[Spoiler (click to open)]And I did wonder why it ended with Danny just about to go through the portal. I would not be entirely surprised if the next book took up right after this one, though it would break the standard pattern.