I'm reading a Call of Cthulhu adventure as I prepare to run the game for the first time, and I keep coming across things like this: "If the investigators check the back issues of the local newspaper, either at the newspaper’s offices or at the local library, a successful Library Use roll uncovers several stories of interest...."
This an example of a frustrating feature of many games and scenarios - a dead-end roll: what happens if the player fails the roll? They go to the library to look for clues about the mystery and..."You don't find anything." This is not fun, for the player or the referee. Players don't like being presented with buttons that don't do anything when pushed. This module comes with several fun handouts of articles that can be found at the library, but if the player fails this roll then the handouts just remain unused behind the referee's screen?
I don't have much experience running mystery games; it strikes me that if the discovery of clues is predicated on dice rolls, then there is the possibility that no clues will be found, leading to a frustrating game. On the other hand, you don't want the discovery of clues to feel inevitable; you want the players to feel they have accomplished something - that their choices have made a difference. I'm not sure how to achieve this, but in the above example it's clear how everyone at the table would likely feel if the player in question failed their Library Use roll - that unsettling what-are-we-even-doing-here feeling when everyone is suddenly thrown out of the game and you think "is this fun?"
Does Library Use really need to be a skill? How is it possible for someone to enter a library looking for specific information and find nothing at all? This starts to feel like a clumsy attempt to cram more dice rolls into a game because rolling dice is fun.
But rolling dice is only fun when there are stakes, and when both success and failure will drive the action forward in some way - "nothing happens" is not a fun result in a role-playing game, in my experience. We're not playing a miniatures game here; it's a mystery/horror story - when a player decides to do research at the library, something should happen as a result, not simply "you missed."