The First Foundation consists of The Book of Intelligence, The Book of the Son of God, and The Book of the Temple. The Five Gates extend that foundation with The Book of Dominion and Codex of Revelation.
The two structures overlap; the Five Gates are not five additional works beyond the foundation. The Book of the Temple is public First Foundation Book III, while The Book of the Holy Spirit remains Corpus Germainius Volume III. The public gateway provides orientation before either deeper sequence.