Kenai by Dave Dobson
A planet steeped in mystery... Jess Amiko is long past her days as a space marine, with all the glory of that time tarnished beyond repair by what came after. Trying to rebuild from the ashes, she's taken a job as a security guard on Kenai, a lonely world far from the Council systems. It's supposed to be easy duty - quiet and peaceful, on a docile world with no real threats, watching over an archeological dig at a site built by a race long vanished. Betrayed and attacked by forces unknown, and finding that nothing on Kenai makes sense, Jess is plunged into a desperate fight for survival that leads her deep into the mysteries of Kenai's past, and deep into the hardship and paradox the planet imposes on all who call it home. Content warning: military-style violence.
Book Length: Long Novel - 320-650 Pages