This book may contain some facts. I happen to think that the allegations about the parentage of some of the Royal Family are true.
However, there is so much absolute nonsense in it that the truths may be overwhelmed by the rubbish. One example is the claim that 700K children in the US go missing every year and are never heard of again. Two minutes on Google tells us that 460K go missing and 97.8% are found almost immediately. I could cite many other examples of poor research.
The spelling and grammar make reading it a real trial. I cannot recommend this.