Here is how to find all books at Godwin Estate:
Mary Godwin’s Diary I
As soon as you enter the garden you will find this book on a bench to the left. Its right next to the Topiary Swan.
Mary Godwin’s Diary II
After finding the closed gate follow the golden trail but stop a bit before the graveyard. This book is lying on the hedge next to the Combustible Northern Monkeys.
Mary Godwin’s Diary III
When you have to protect the generator look to your right to see some crates with a torch. Check behind these crates to find the book on top of a smaller crate.
Mary Godwin’s Diary IV
After defeating the hobbes and entering the 'indoor graveyard' you will find this book at the end of the room on a table to the left of the red structure.
Mary Godwin’s Diary V
After defeating the second group of hobbes you will go down some stairs and see some weird gold/green/red containers. The book is on the right next to the 2nd container.
