This can be a politically scary book because of potential misuse by ideologues to expose the faultlines of the Indian society. Nevertheless,for a rational person it is a good read (pun intended ofcourse).It goes into details of various Dravidian deities(aka Sakti) and how over time they've been incorporated into the Hindu pantheon.
The modern Hindu religion is,in fact, a fusion of Brahman and aboriginal beliefs, and the position which either set of beliefs holds in the religion of a particular caste is determined by the position of the caste. This fusion appears to be occuring at a rapid pace now,as the grip of the obsolete caste system on the society is weakening.