From the back of the book:
"Investigator fields manual
This book contains the Field Manual of the Theron Marks Society, a secret organization that from 1920 till 1925 fought the awful cthulhoid manifestations worldwide. This manual includes all the investigative techniques and the hints necessary to defeat cruelest horrors than conjure in the shadows: this is a real scripture that every occult investigator needs. Furthermore, in the inside you'll find an useful appendix that will help you solve all the frightening mystery
'Normal people don't spit you back bullets you shot!'
This rare italian book collects "Field Manual of the Theron Marks Society" from Terror from the Stars , "The ten Commandments of Cthulhu Hunting" and "Sinister seeds" from Cthulhu Casebook.