first off, i love that this solo adventure is free on this site, it is offered in the Starter box set so it makes sense to have it free for all to try out Call of Cthulhu.
now, the adventure itself is a really great introduction to the game and the theme of Call of Cthulhu, it's set in 1920s and the mystery is really good.
it's written as a choose your own adventure style that you read yourself, or one suggestion is that you read it out loud to one player and tell the story that way too.
this module definitely requires you to have a character sheet and some dies to roll, because the first couple of sections it walks you through the character creation process akin to Oblivion, Morrowind if you played those games. it's done well and the skill checks are well placed as it really gives you an idea of what to roll, how to read the character sheet and understand the setting.
if you don't have a group to play the Quickstart adventure The Haunting and want to try out Call of Cthulhu this is a great way to try it out, and to give to friends who want to play it or you can and play with as well!
for the low low price of free, whats there to lose?