there are a ton of books on the japanese holy trinity and several on the lesser known heads, such as the WW monograph on jun takahashi / undercover. sadly for us westerners, most of the interesting books and magazines i came across during the dissertation research are in japanese. i found many in the idee bookshop in aoyama. the WW monograph is in english, but i don't know where to get it (got mine at idee).
i would start by hitting up cultish design bookshops - architecture bookshops (like form zero, henessy + ingalls, untitled) or japanese bookshops (like zakka, kinokuniya, mitsuwa) are a good start.