The best book I've read about private equity is called Songs of Profit, Songs of Loss by Daniel Souleles. It's an ethnography of private equity.

Private equity is the logical extreme of the idea of shareholder value. Companies are bought, stripped for parts, and mined for resources. The money comes from wealthy people and institutional investors like university endowments, pension funds, etc, and some years it is a very high-return investment. Other years, not so much, see the relationship by the University of California and Blackstone as an example in recent years.