Adventure Quest: "Select Your Own Endeavour"
During "Bored to Death", you will fight a skeleton which will come out of a crypt . Defeat him and go inside to find the book .
"Dangerous Things: Lightning"
Go inside the Reaver's mansion and head to the room on the left . The book will be lying on the table by the window .
"Liver of Darkness"
After completing "Hobnobbing with Hobbes", wait a couple days and return to the cave . To find the book, stick to the left side. This way you will reach an underground lake .
Enter it and swim to the far left. On the small fragment of land there will be a table  with a book lying on it .