To follow up on my first impressions post, I wanted to provide a slightly more detailed review. That said, there's honestly not a whole lot to review. The fluff is interesting, but no huge revelations. The biggest notes of interest for the fluff is the brief mentions of other Ordos, including Chronos and Scriptorium. That said, all the new Ordos are mentioned extremely briefly.
As far as the rules themselves, to begin there are three "unique" tables, one for each major ordo, Malleus, Hereticus, and Xenos. That said, 1-3 are the same for each. The other three traits are relatively unique, though 4 is Preferred enemy depending on the Ordo; Psykers for Hereticus, Daemons for Malleus, and all non-vehicle units from all Xenos codices. As a result, by a fine margin, Ordo Xenos seems to have a slightly stronger selection. 5 and 6 for each Ordo allow for a couple minor special rules.
Of the three ordo Inquisitors, each have slightly different options in weapons in equipment. For example, only Ordo Malleus Inquisitors can swap out basic equipment for Terminator armor. Ordo Xenos Inquisitors are able to use some Xenotech weapons.
As for the Henchman units, there are plenty of options to allow for plenty of choices. As a single unit you of course will have to balance the usefulness of mixed uses within the unit. I'm not sure what the best option would be, but I'm interested in the idea of having a henchman unit of nearly a dozen psykers. A single psyker's power is only S3 AP6 Large Blast, but with 8, the power becomes S10 AP1, Large Blast. Frankly, that's pretty impressive, particularly at 80 points. At that price cost, I would be willing to get a couple extras just for redundancy, particularly if I decide to get them a Valkarie. Having a couple extra psykers allow for me to risk Grav-Chute insertion while the Valkarie is Zooming along. For about 200 points, I have a fast, mobile gun platform that can drop off a huge tank/terminator destroying unit.
In all, I like the flavor of the book. I don't think I could see using it as a primary force, but as an extra allied detachment I think it can be effective. Depending on your Imperial force, there's enough flexibility in henchmen units to build a complimentary unit or two.