The Pranava Vada was written by Maharshi Garagyayana
It is an extremely rare book explaining everything in the Universe/Samsara and its relation with AUM. It explains everything about the pranava AUM and its different meanings,its importance.In short the author of the book gives connection to everything in universe to AUM or it says everything is AUM( or orginated from AUM)
This book is a available on the link provided, its available in ENGLISH only.
http://www.makara.us/05ref/01books/pranavavada/pv_toc.htm