Two books are part of the set of Hunter Must Haves.

I have one of them called the The "Supernatural" Book of Monsters, Spirits, Demons, and Ghouls. It's full of important facts on every thing you'll want to hunt, witches, monsters, legends, zombies, all of it. It's important to any Hunter, I know I use it on my travels.

The second comes out in the new year, its Called Supernatural: John Winchester's Journal, and it's either a story of John's Hunts, or its a literal recreation of John's Journal used by the guys in the show... either way its a must have, full of stories of monsters and demons.

Add with that the In The Hunt: The Unofficial Essays on Supernatural and The Supernatural Companions of Season 1, 2, 3, 4. And you're ready for a life of Hunting.