It occurs to me you can rate other works of literature by how many characters need to be replaced by ninjas to make it better. For example, for other recent reading:

Shelley's Prometheus Unbound - Would be improved if either Asia or Panthea was a ninja -- I'm not sure which would be better. Both wouldn't work, though.

Byron's Manfred - The whole bleeping cast needs to be replaced by ninjas (except for the spirits, who'd have to be tengus). And then drop-kicked off the Jungfrau.

Keats's Endymion - Ninjas would be superfluous.

This gives them ninja-replacement scores (NRS) of 1, ∞, and 0, respectively. It also works with prose -- Lord of the Rings has an NRS of 0 (the only possible improvement is ninja!Sam, but that wrecks the last line), while Pride and Prejudice has NRS = 5 (arguably).

Care to rate any others?

ETA: Ninja-replacement in Shakespeare is being discussed here.

---L.