[quote=@Lonewolf685]
I wish there were more books on them. I would love literature on their founding, the Titan Legions, Marian Civil War, etc.
[/quote]

There's a book written about the Martian Civil War during the Horus Heresy. It's called Mechanicum by Graham McNeill.

Anyway yeah, seems like a tech-priest is a great niche to fill in any Inquisitorial retinue.