Yu Yu Hakusho. The episode you're referring to is epidode 9.
Sam Anderson has appeared in many television shows and movies. He is a character actor. Some of his more famous roles have been in Forest Gump, Lost, ER, and Dallas.
If you are referring to the episode in season two, "Who Mourns For Adonais?", the character in question is named Apollo, and was played by Michael Forest who appeared in several TV shows in the early 1960's.
The Enchanted Forest!
Aokigahara Suicide Forest - 2010 TV was released on: USA: 2010
Amazon Land of the Flooded Forest - 1990 TV was released on: USA: 10 January 1990
Appalachia The Endless Forest - 2005 TV was released on: USA: 2005 Hungary: 6 January 2013
Super Night at Forest Hills - 1977 TV was released on: USA: 9 September 1977
1st star (4th character) - Forest Frenzy2nd star (5th character) - Snow Dragons3rd star (6th character) - Ogre Forest
Music from the Heart of the Forest with Peter Davison - 2013 TV was released on: USA: 1 January 2013
Beyond Sherwood Forest - 2009 TV is rated/received certificates of: Australia:MA (2010) Portugal:M/12 Singapore:PG USA:TV-14
New York Television Theatre - 1965 Save Me a Place at Forest Lawn was released on: USA: 1966
If "The Book of the Forest Spirit" is a part of the TV show "House of Anubis", I can not find mention of it in the Wiki of House of Anubis.