We've known what this card's effect was going to be for a little while, and it feels like maybe as a result its slipped under people's radar a little with all the exciting new cards being revealed.
I tend to like to evaluate cards in the context of existing cards that do similar things, or at least fill the same role. In the case of Scroll of Secrets I feel that it kind of demands a comparison to the core set's Old Book of Lore. Both are seeker tomes taking up a hand slot, both give you an action that lets you look at 3 cards and draw 1.
However, Scroll of Secrets costs 3xp to the OBoL's 0, and only has limited uses at that. To make up for these downsides, it costs two fewer resources and gains some pretty interesting additional utility. It's pretty unlikely that most people would consider a 2 resource discount to be worth limiting the uses to 3 and upping the level to 3, so we have to look at what benefits the particulars of the cards effect bring.
First of all, the OBoL lets you choose one card from the three and then shuffles the other two back. The Scroll lets you make a few more choices. It allows you to choose to discard one of the three cards, this lets you get rid of a weakness or a card you dont want to see this scenario. Or even, for example, discard an Insight card to hit with Eidetic Memory. Additionally, the scroll lets you put the card you dont draw or discard back on the top or bottom of the deck. This means that if you see two cards you want, you dont have to shuffle one away. You can draw one now and put the other on top to draw at the end of turn. Putting a card of your choice on top also allows you to dodge drawing a weakness for that turn. I think the power of this effect shouldn't be underestimated, allowing you to actually start to thin out your deck and control what cards you are going to draw is a huge benefit over what is essentially just an upgraded draw action on Old Book of Lore. The power of this effect also clearly justifies the limited uses, otherwise you would be able to delay drawing a weakness indefinitely.
The second option that the Scroll of Secrets provides you is the ability to use it on the encounter deck. This acts similarly to the much maligned Scrying, only with similar benefits to those outlined above. If you see a card you really dont want to deal with such as Ancient Evils you can just get rid of it. It also lets you place a non-enemy card on top, which in solo could be a huge benefit. I think this mode is significantly weaker than using it on an investigator deck however, since in Solo you are unlikely to have the actions to be using this when you most need it (ie when you're already engaged with an enemy or dealing with a tough treachery). While in multiplayer you are only changing the encounter drawn by a single player which is only marginally beneficial in the best case. It is always nice to have this option though.
In terms of investigators, this is obviously good for Daisy Walker for all the same reasons Old Book of Lore is. Given how core that card is to her general strategy, I feel that this would be worth it even if it was just a third or fourth copy to improve her odds of drawing it. As it is, having all the benefits that I outlined above I think this card fills it's own niche in the deck and provides a lot of new potential power. For other investigators I do think this starts to look a little less appealing, Minh Thi Phan already draws enough cards that she doesn't benefit much from an upgraded draw action once per turn. Ursula Downs is good enough at both investigating and dealing with enemies that she can usually profitably use all her actions as it is, similarly for Joe Diamond. I think Rex Murphy is the only other investigator who I might consider taking this in, if only for the fact that it lets you actually get rid of his weakness for good.
Overall, I think this another solid addition to Daisy's library, and an interesting niche pick for investigators that are worried about drawing their weakness.