Source books and other referencesEdit
The Fifth Edition material on the Divine, including both the power of the Divine and its agents (mechanics in the game) and information about the three major religions that notably worship the Divine- Judaism, Christianity, and Islam- is largely in Realms of Power: The Divine.
The mechanics of Divine power, particularly with regard to magic or diving power used by mystics within both Judaism and Islam was one of the major reworks in the making of the Fifth Edition. Thus, there are two uses for source books from earlier editions. Where they do not contradict the setting as presented in Fifth Edition, they can provide expansive material that did not make it into the 144 pages of the Fifth Edition book. Where they do go against the purpose of the Fifth Edition changes, they offer possible variant rules and world mechinisms that can be fused into your saga.
In its Fourth Edition run, Atlas provided two sourcebooks that covered the two religions that were in the mythic Europe, Judaism and Islam. Kabbalah: Mythic Judaism is a sourcebook dedicated entirely to Mythic Judaism. The Project Redcap FAQ gave mostly high mid range ratings, but two criticisms were prevelant- that the topic is very narrow and that it makes clear that a devout Jew or Jewish community would not having anything to do with Hermetic magic or magi. As to the second critique, see the Mythic Judaism article for some ways to deal with that. Otherwise, if you want just a smattering of information, the Realms of Power: The Diving should be good, but if you do want more, Kabbalah: Mythic Judaism is worthwhile.
Though a tribunal book, because of the location it covered, Blood and Sand: The Tribunal of the Levant provided a good amount of material on Mythic Islam and a specific Islamic mystic called a Sahir, whose power came mainly from their ability to summon various spirits to do their bidding. Admittedly, as presented this first time, it seemed to push the ability of Sahirs to break Hermetic limits.
White Wolf published one sourcebook in the Third Edition, Pax Dei. The bottom half of the ratings provided by reviewers in Project Redcap outnumbered the top half of ratings by three to one. This work also led to what is possibly one of the most succinct criticisms of one of White Wolf's major flaws at times, to wit that the work "Suffers from the White Wolf pathology that says all attempts to structure society are corrupt, and all who follow an ideal are dupes or con artists."
Other sourcebooks include some things that are or can be related to the Divine. The House Ex Miscellanea section of Houses of Hermes: Societates presents to traditions that are or can be more connected to one of the major religions, if not the Divine itself. The Donatores is a recent tradition that formed when a group of banishers and exorcists, previously spread out and unorganized, converged on a site of major activity of ghosts and walking dead. The Order became aware of this and brought them into House Ex Miscallanea. The other group are the Iberian safirs who joined House Ex Miscallanea, but only after the death of Flambeau. That material states that the hermetic safirs are not necessarily the same as their counterparts in the Levant, and there is not yet any Fifth Edition material on those safirs.