I got this card in my recent campaign as Minh Thi Phan, and it was awesome. Playing it with Scavenging (2) you can basically convert 1 resource into 2 cards. It can even be the resource you just got from Dr. Milan on the same test, because both abilities trigger at the same time. Then use Pantalone to punch some Rats, pick a Locked Door, evade an enemy or just discard the card to a treachery like Crypt Chill. Rinse repeat on the next test with Deduction (2), Perception (2), Sharp Vision, Archaic Glyphs: Guiding Stones...

Try it out before the next Taboo list will remove this card from the game after use!

You ever say to yourself "I want to attack with ALL my stats" well right here we have for you today a grand special deal.

Roland's Enchanted Butterfly Knives of the Mind! (over matter)

Never again have to think about which stat does what, just add them all together and blast your opponent with them!

So, this card is pretty great. It isn't cheap (3-cost, 3 XP), but it ends up reading pretty close to "you draw an additional card each turn" + "you get +1 skill value to a random test each round", and you could do a lot worse than that.

I don't usually consider how many icons are on my assets, but if you are running this in a "regular" Mystic, it may be worth upgrading that Shrivelling to Shrivelling pretty quickly for that extra icon. Generally, I assume you'll use the first every round, and then find tests you are pretty likely to pass to get the cards into your hand.

However, one exceptionally powerful use of this card is with the new signature asset for Norman Withers, Livre d'Eibon. Use Livre d'Eibon to put a skill from your hand on top of your deck, then attach it to the Astronomical Atlas. Then, take a skill test where you can commit that card and get the benefits. When that test ends, you get the skill back, and you can repeat it the next round. Who would like a Deduction or Perception every round? Norman would.

Schoffner's Catalogue isn't a good card on its own. The reason is obvious; having to pay 2 resources, a card and a play action for 5 resources is a lousy deal. Yes, you can pay for other investigators' stuff, but the item assets-only clause is a severe limitation in a game with events, spells, allies and whatsnot. Also note that most investigators tend to play their items early-to-mid game, making Schoffner's Catalogue less relevant as the rounds pass by.

Still, it's a good card for a few investigators:

• Bob Jenkins really likes this card, as he can play it as an extra action and use it to pay for all his other items. The catalogue as an item based support package is literally designed for him.
• It's also decent for parallell Daisy Walker, as the catalog is pocket sized and requires no hand slots. And =Daisy can use it to pay for her other tomes and as a target for tome-related shenanigans.

Other highlights:

• Recursion. The catalogue is automatically discarded when empty, making for an easy combo with Scavenging. With Scavenging (2) you can even get it in play without spending a play action.
• Tome interactions. Whitton Greene to find it, Library Docent to bump it or play it for free, etc.
• It's also a possible source for harvesting secrets (Eldritch Sophist).

All in all, a niche card that works well for Bob and possibly parallell Daisy. Other investigators will have to find ways to make the catalogue more efficient to make it worth their time - such as a support Minh with Scavenging or a Yorick build with enough costly items to make the catalogue worth using his ability on.

Q: When no more set-aside Monster enemies left, can I trigger action ability on this card to discard?

RR "Target" says :

The term "choose" indicates that one or more targets must be chosen in order for an ability to resolve. The player resolving the ability must choose a game element (usually a card) that meets the targeting requirements of the ability.

If an ability requires the choosing of a target, and there is no valid target (or not enough valid targets), the ability cannot be initiated.