The Hardly Haunted Library is a great one-shot or side-quest that can easily be dropped into an existing campaign. I actually just received my copy of Curse Of Strahd Re-Vamped today and am planning on subsituting The Hardly Haunted Library for Death House as my player's first supernatural encounter and gateway to the lands of Barovia.
The Hardly Haunted Library is heavily weighted to accomplishing tasks and problem solving and runs light on combat. Having said that the inclusion of a full-page map that appears to be well scaled to use as a tactical map will make combat super smooth and easy to run.
The narrative is interesting, satisfying, and logical. The haunting elements are also effective without being jump-scares and in addition to my regular players I think this is also and adventure I can run for my 13 year old.
The adventure is admittedly fairly short, but it works well that way and is certainly still a bargain for the price! I definitely recommend this to anyone looking for a fun introductory adventure with a supernatural flavour.