Yeah, I was doing that originally, but I condensed it into one book. Right now it's all chapter based to split things up. Once I get things more setup and all I'll split up the books. It's just been difficult for me to constantly have to swap books to write. Eventually I hope to split between a Codex (Fluff Tastic), Player rulebook, and GM rulebook, but I need to have sufficient content to justify the splitting. Understand the issues with accessibility, but it's a lot simpler to add content to a word processor.
Primary Influences?
Combat, weapons, and a few aliens are influenced a lot by X-Com (The Old one.) I made an simple combat heavy Online Tabletop type RPG a while back based off x-com rules modified slightly. The math for it was pretty good and applicable to board game type setting oddly enough. A few armors draw a little on x-com, but most armors are more based off my own thoughts and research.
Psychic Work and ancient evil stuff is influenced by 40k a great deal, though I've modified it to make it tad more ... fitting with the setting. Plus I wanted to add the whole enhancement type psychic sets. A few psychic powers were influenced by Stalker monster abilities.
Space combat and the whole sub-space idea was influenced heavily from Freespace and those things. I also draw from some other 4x games when doing the designing for the space navies and the things for space, but since it's not been a focus of player play, I haven't really put a lot of detail into it. I'll probably add more in time.
A lot more vague influences here and there. Mostly games are big, but I like to give a decent post-cyberpunk feel to most of the larger urban areas, a more sci-fi western feel to frontier settlements, with other types of sub-genres of sci-fi sprinkled in. I like to keep the setting firm enough that there's clear races, relations, and technologies, while being loose enough that you can have a focus of a sci-fi type of western and someone else can focus on sci-fi feudalism without needing to leave the setting.