Probably one of the worst signatures in the game, it gives you an increased hand size which is the only thing saving it from the trash bin. There are major flaws with this card that need to be addressed.
A: you can only use this if you pigeon hole yourself into the role of clue gathering, which means to even get to use this effect you have to be willing to discard every other viable action you could do with Harvey, seriously! being forced to investigate every single round can really force you to be stuck where the clues are and away from the action.
B: its benefit is actual a downside when you think about it, so besides it amazing ability to hoard cards it also makes you draw cards from your deck, every card taken from your deck just gets you closer to a weakness and an eventual horror damage, its not worth speeding up that kind of doom clock, you use this too much and you may end up losing half your sanity just because you drew cards. (and if you use Harvey's ability you end up doubling the speed of your own demise)
C: it can grief your teammates... Unacceptable. You can force a teammate to draw weaknesses, discard cards from their overstuffed hands and take horror damage as you repeatedly get them to draw through their entire decks, I can't imagine any player ever wanting to play alongside a Harvey and seriously disrupting the natural rhythm of their deck to a faster more dangerous beat.
Side note: while its icons aren't good (triple fight would allow you to use strange solutions on bosses more regularly) the real killer is even if you try and get rid of this card Harvey's natural ability will likely make you just draw it again, especially if you are sensible and try and commit it when your deck is near empty and need to rid yourself of its vile temptation/S.