I originally purchased this supplement as a hardcopy some time after it was published in 1989. My intent was to run it as a campaign, but due to the exigencies of my gaming group, I would up running a couple of the scenarios as interludes in another major campaign (Shadows of Yog Sothoth, to be precise, but that's another story). Over the past 20 years, I managed to lose my copy, much to my regret.
I was delighted to discover recently that DriveThruRPG was offering this item as a PDF, and hastened to purchase it.
Overall the contents of this supplement are simply outstanding. Each scenario is dangerous, challenging and exciting right through to the end, with enough red herrings and potential future plot hooks to almost ensure a smart keeper can tie them in anywhere in his campaign plan. Each scenario also provides tons of material to help the Keeper play them well -- slang lists, vivid descriptions, and enough variability so that the players and Keeper are not forced into some kind of linear play routine -- making the players feel that much more in control. In addition to the scenarios there is the introductory essay which could easily serve as a speech given by one of your NPC's to help educate the investigators on the "Cthulhu Mythos" early on in your campaign, an incredibly useful "universal calendar" that can be used to help plot your gaming time-lines for various scenarios in any era you're playing (in my opinion, the calendar makes the book worth purchasing, all by itself!), and even some foreign language character sheets which were the very first effort by Chaosium to broaden the player base beyond the English-speaking world.
This PDF version easily earns a "five." It is very clearly reproduced, with not difficulty reading any parts of it. The illustrations and handouts (which are also reproduced separately at the end of the book) are easily printable and copy-able with no difficulty on the part of the Keeper. Best of all, I managed to purchase it for about two thirds what it cost as a hardcopy in 1990 (when I actually bought my original copy). The only difficulty I had was with downloading the file. Thanks to my ISP, I was prevented from using the normal links to do the download, however DriveThruRPG's superb customer service department worked with me all day to try and rectify the situation, and finally provided me with ftp links to download the products I was having trouble with. Fantastic job on their part and a big tip of the hat to Jeff Montgomery of DriveThru's customer service department -- he turned what could have been a complete disaster into, well, an experience that I don't regret! All in all, a big two-thumbs-up for DriveThruRPG on an excellent reproduction and superb customer service!