Subterranea: Empire of Wrath

From publisher blurb:

There is another world beneath the ground... A realm in miniature that normally goes unnoticed... Unless, that is, you were somehow reduced to the same size as its denizens and then trapped within that very same underground world! This is exactly the position you unexpectedly find yourself in ― where insects are now lethally large, a pin has become a blade that could save your skin, and the usually unseen predatory rivalries that affect the daily lives of those that dwell below are suddenly a matter of life and death...