Buy this if you have Stella Clark in your team and enjoy committing Neither Rain nor Snow. Same goes with Nautical Prowess if Silas Marsh has managed to drop it.

Other than this, my favorite targets are Daring, Vicious Blow, Deduction, Brute Force, Expeditious Retreat, Sharp Vision, All In, Defiance, Fearless.

EDIT: Signature cards cannot be controlled by anyone other than their owner. Copycat cannot be used on Nautical Prowess, Neither Rain nor Snow.

There’s a reason the individually packaged investigators can only take their color and neutral cards… Because they’re amazing at what they do. Harvey is the epitome of the big hand seeker, with almost every card he can get either helping him gain cards or helping his hand size, or taking advantage and discarding cards for effect. The man is a mobile library, and while you could play him with magnifying glasses and Hawk Eye cameras, he’s designed for books. Piles and piles of books. Celaeno fragments, forbidden Tomes, Occult Lexicons...

What separates Harvey From Daisy or Norman, however, is that he works extremely well with teammates. His ability can trigger off of others. He can gift cards with his signature card while doing actions he already wants to do, or simply be around while Winnifred or Nathaniel handle their business. It’s important to have focused characters you can give to a new player, and if they are playing Professor Harvey, they are going to be able to have fun and contribute to the game.

Plus: Tempt Fate for 2 cards in 0 actions.

tl;dr Well Prepared, Archaic Glyphs (Guiding Stones), The Necronomicon is a crazy combo that can trivialize clue-gathering.

In longer form...

This card is a core piece of my favorite Arkham LCG deck: Joe "The Book" Diamond. It's a basic three-card combo deck that can perform absolutely mind-boggling feats of clue-gathering and save tons of actions.

So we've got the Nomnomicon. What's the rest of this combo? It's pretty simple, but at the time of writing only Joe can pull it off. You just need Archaic Glyphs and Well Prepared! With the Necronomicon this comes out to 15 XP total. Triggering Well Prepared on the Necronomicon gives you +5 to Intellect, which with nothing else is already a 9-value stat. Assets and other commits, as well as skill boosts from the Necronomicon, can easily raise you enough to pick up 3 or more clues reliably per action.

Plus, this card just straight value in Joe. It supplements free clues from his Hunch deck, damage against enemies, and can be refilled/used for free via Truth from Fiction, Astounding Revelation (if you're running searches), and Knowledge is Power.

You won't always need to spend four Nomnomicon charges, exhaust two copies of Well Prepared, and commit four Intellect icons from hand in order to succeed an Archaic Glyphs investigation by 23 and pull 12 clues off of a single location with a single action. But when you do, the Well Guided Necronomicon is here to help!

Sugar Granny has gotten a lot more tempting with Cornered being part of the Survivor cardpool. In Yorick, who likes to pitch assets to Cornered and then replay them a lot, he can often run low on both cards and resources. Madame Labranche is very versatile in such a build, helping you replenish whatever you're short on. As a bonus, she's fairly inexpensive herself and has decent soak, so she fits well into a Yorick tank build.

The only question that this card needs to address is the situation in which (spoilers: After reaching to Act 3 and Agenda 3, how do you activate this ability?). The text reads to Move 1 doom from one agenda to the other, but if the second agenda does not exist, how can you use this ability, see "Then" keyword in rules reference. It is possible for you to never enter an additional location by spending the requisite clues if you cannot use this ability later on in the game. This card may need to be errata otherwise you will never be able to receive the necessary amount of clues to advance the act deck.