Preternatural Days is a great introduction to the PROBE team, and generally what life in PROBE is like.

Following a new character with no-prior associations with PROBE, as his life is thrown when Giles steps into his life reminds the reader a lot of stories like Rose or Everything Changes. Rose especially seems an apt comparison to me with Az's workplace being the hideout for a cult, the story ending with him being put out of a job, before joining PROBE, being fully whisked into the world of myths and monsters.

However, the sections we get from Giles' perspective, and Az's view of PROBE HQ really help to set the story apart. PROBE HQ isn't The Hub, with it's alien equipment, it's labyrinth of tunnels and storage, and it's extreme level of security... it's a small office in Whitehall. Giles isn't The Doctor, adventuring around, the eternal traveler, never worrying about where they're going or how they're making a living... he's a government official. This is his job, and he's struggling to keep the department going.

The actual threat as well also helps make this more unique, Torchwood and The Doctor deal with aliens and monsters. PROBE deals with necromancers and cultists.

Finally, there's a few really fun continuity nods in there, Miracle Day, Doomsday, and Face The Raven are all subtly hinted at, and I really enjoy them.

Overall, a strong start to the collection.