Saiyuki

If you love manga, Saiyuki is definately a series to invest in. I've read all of the first series and the first book of the second series (the second volume I can't get my hands on...). I really suggest reading the manga first instead of seeing the anime. Alot of interesting and funny jokes and facts are lost in...translation. ;) Plus! The manga has fantastic art work. Yaoi fans, there are hints...but...*shrugs* they leave it all to your imagination. Wishful thinking I suppose.

From Wikipedia

Saiyuki, also known as Gensomaden Saiyuki (幻想魔伝最遊記 Gensōmaden Saiyūki?, lit. Romanticized Tale of a Journey to the Extreme) in Japan, is a popular manga series created by Kazuya Minekura and loosely based on the famous Chinese novel Journey to the West (Xī Yóu Jì). Studio Pierrot has adapted it into an anime as well, although the storyline is not yet complete.
Gensomaden Saiyuki deals with the fortunes of four fighters - the monk Genjyo Sanzo (Romanized Genjo in the anime and Singapore English manga), the monkey deity Son Goku, the half-demon Sha Gojyo (sometimes spelled Gojou), and the demon Cho Hakkai, who have been dispatched by the Sanbutsushin (The Three Aspects of the Buddha) to India to investigate the reasons behind the recent insanity among the demons. Demons, who have formerly coexisted peacefully with humans in Shangri-La, are going berserk and turning against them