From the back of the book:
Take a glimpse into the Golden Age of Witchers, when monsters roamed the world and you could hardly travel to the next town without running into a cyclops or a foglet! Through the journal of the founder of the Griffin School of Witchers, Erland of Larvik, you'll encounter many new monsters; some of which haven't been seen in generations.
A Witcher's Journal is a supplement for The Witcher Pen & Paper RPG which gives you a number of new monsters and intriguing plot hooks to use in your game as well as new lore and an indepth investigation system.
33 New Monsters: Terrorize the countryside with all manner of creatures, from deadly archespores to gruesome vedigo!
2 Exceptional Monsters: Create unique higher vampires and true dragons to populate the dark corners and high peaks of the Continent!
An Indepth Investigation System: Learn how to write out a mystery for your players to uncover as the game progresses or write up a murder mystery for a session of fun!
All New Lore: Learn the history of the Order of Witchers ad the story of Erland of Larvik, the first Griffin!