Simply put, the mechanics of this adventure are broken. What should be exciting roleplaying opportunities are reduced to an endless series of skill tests so abstract as to render them meaningless. The only investigation section revolves a single -20 Tech use test, which if failed removes any option other than brute force. Without a tech-priest in the party there is no way to access most of the story, since everything needs mind impulse units to access.
If you do not intend to play the adventure as written, but instead to write your own missions around the events and setting, be warned that even that isn't up to the standard set by the first two. Where they explored some of the most interesting and unique aspects of the setting and had many memorable events and characters, this is 40k at it's most bland. Cultists are crazy and summon daemons, kill them. That's really it. The conspiracy behind the first two adventures has disappeared and you never deal with them; the only possible mystery is something the players witnessed themselves in the last adventure; and the man behind it all has already been defeated. The resolution violates the lore in pretty severe ways that I won't spoil, but if you've even read the background in the core rulebook they jump out at you.
I have run the entire trilogy as GM, and this is a huge drop in quality from the first two which had none of these problems and which I highly recommend. According to the credits page most of the same people wrote the first two, while this entry had a single author who was involved in neither. While I recommend the trilogy as a whole, I suggest you skip this chapter and make up your own ending.
[1 of 5 Stars!]