Tom Gauld has a new collection of literary comics out, You're All Just Jealous of My Jetpack. It contains a number of mystery-related comics. Here are some of them:
One of my favorites, "Some of My Forthcoming Mystery Novels," doesn't seem to be online. It includes illustrations and sample dialogue from Easily-Distracted Cowboy Detective, Overly-Dramatic Astronaut Detective, and Catty Unicycling Detective.
As it happens, he also has a number of library-related comics, like this one, and writing-related comics, like this one. And science fiction comics, and poetry comics, and electronic reading devices comics. All great comics.
Long live Tom Gauld!