Read Rin's Kaiho Fuseki dictionary, Nihon Kiin's Fuseki Encyclopedia (if you can afford it), Fuseki Dictionary by Takagawa Kaku, Modern Opening (Kweon Kyeong-un). Unfortunately, I am not aware of any noteworthy theory book on the opening for dan players. All these books teach by examples, but at least they are good at that. Note that you learn little on modern openings from these books; study the openings of modern pro games for that purpose and appreciate flexibility.