It is a fictional psychology book with no scientific data to support his ideas or conclusions. Many of his ideas appeared earlier elsewhere. Although the book was popular when it was first published, Hubbard eventually went bankrupt. He re-envisioned his ideas later with Scientology and called it religion, so he could obtain tax-exempt status. He successfully coned people into paying for his courses. It appears that the so-called religion is dying out now, although it still has loads of money.