This card is great.
At face level, this is not a bad level 0 card, you can get a bonus trigger from a combative spell like Shrivelling or clue spell like Rite of Seeking without paying any resources to put it in play or even spending an action. Pushing the limits to make 4 attacks in a turn is a great ability on it's own, well worth a card, but when you start upgrading cards and using this to key off-of them it becomes outrageously good.
4 Shots from Shrivelling to deal 12 damage in a turn, normally something not possible without very big guns combined with cards.
Trigger Encyclopedia as a fast action, to gain that bonus to a combat relevant ability and use it to win a fight.
The sneaky bit of goodness to this card is the ability to hit cards in your hand as well, you get a chance to oust yourself from scary situations by calling upon assets you havent got in play yet, this is especially useful at the start of a scenario or when the mythos deck is killing assets or resources.
It also gives you leeway to play with an overloaded slot ( characters tend to have an overabundance of Hand items, characters have trouble with Arcane slots). While your hands or Arcane slots are full you can snipe a card in your hand, possibly saving charges on something, whilst also refunding a potential dud draw.
The biggest issue with Knowledge is Power is it's class. It's a decidedly card that's printed yellow. Which limit's it's extreme power, which I guess is fair, if this card were it'd be a contributing factor to making Akachi Onyele and Agnes Baker the uncontested best characters in the game.
The standouts who get the most from Knowledge is Power are:
Norman Withers, he needs to make use of his level 0 to do a lot of work, and this card definitely helps him stay relevant while he is still skilling up Shrivelling and makes him an outright powerhouse once he's got just 10 XP. The way Norman powers through a deck with his ability, you can get all of this goodness set up at breakneck pace.
Luke Robinson, he's fresh off the presses so I dont fully know all the options, but he has native access so he can get the fancy Tome shenanigans going that Norman cannot. I still think Norman's raw draw power wins out in the end. Also he can do some interesting teleport spellcasting. Think Mists of R'lyeh blasting an enemy engaged with a friend at another location or Rite of Seeking nuking a location from his pocket dimension.
- Marie Lambeau has very few / slots, but spending 2 of them on Knowledge is Power is perfectly viable. Slower then Norman gut good nonetheless.
P.S. Daisy Walker, Rex Murphy and Finn Edwards can do some stunts too, but it's coming at the cost of precious slots or locked to triggering on 0 level spells, sure you can trigger it on a big book like Pnakotic Manuscripts but really, that card doesn't hold a candle to beasts like Shrivelling or Rite of Seeking.