Until end of turn, it gains hexproof, reach, and "Whenever this creature becomes tapped, it deals damage equal to its power to up to one target creature." Untap target creature
Personally, I lean more towards the two Tomes as being the most useful for most decks, while Book and Mine are both situationally better.
It's the fact that she doubles your creature death triggers
A coded system that relies on obscure symbols might be advertised as being impossible for your spectators to figure out
The Zoro Gold DON climbed from approximately $260 at release to $525 currently roughly doubling in value over 20 months
With that background, Ill present different points of view depending on what game mode(s) a Magic player may prefer, which I believe is one of the key reasons why the Too Many Cards question lacks a universal answer