The Cthulhu Casebook
This book is a collection of some aging Call of Cthulhu adventures¸ most of which seem to be from the very early years of Call of Cthulhu - probably back when it was 1st or 2nd edition. For somebody who's interested in seeing what scenarios were like back then¸ there's nothing wrong with that¸ but it's nowhere near the quality of adventures that have come since.