it involves a magic book and a secret that the bad guy keeps carefully hidden. Works out as dramatic as it does in the fairy tales. There's only one small complication:
The hero has to know how to shape change for it.
Our hero is an ordinary young man. Our heroine is an ordinary princess, and not even one kept captive by the bad guy long enough to have learned his magic. And if he learns it early, or even in the middle of the story, it will throw everything off. If you can turn into an eagle, journeys over wilderness are not so onerous.
Hmmm. . .perhaps it will be a wedding gift, and he and the princess can jest about how useful it would have been.