A great illustrated guide to lovecratian creatures. This is not a game mechanics or monster stats book. Rather it takes the form of journal entries and encylopedia style descriptions of the major 'things' of the game. Art is beautiful and the information reads a bit like a zoological book. It this required for the Calll of Cthulhu game, no. Would it give Keeper's more information and better art to show investigators, yes.
I think the price was a bit steep for what it is and the fact it is a PDF. Luckily I recieved a free one when I bought the book.
[5 of 5 Stars!]