[Well, Hiccup's not an expert on magic. But he's still going to call any magic that curses him 'bad']

Oh, you never know. Maybe someone was really bored. Or they just like to curse people. I'm not exactly an expert on why witches do what they do.

[But Hiccup seems to be satisfied that the book isn't going to hurt him - or at least, he's hoping really hard that it's not going to hurt him. Very, very carefully, he picks up the book and holds it in front of him. Now Loki can see Hiccup's worried face, with Toothless curiously peering over his shoulder]

Well, I wouldn't exactly call Toothless 'sweet'...and he hasn't always 'behaved' either...