Not substantiated by much factual information. When data is presented it's selected to make the point, distorted or incorrect. Easily verified examples on p31:
Author claims that in 2017 president and vice president: 100% white. This is correct, but with a sample size of 2 one must consider a longer time span. Since the 60's, 8 of the last 60 years the president was black.
Claim that in 2017 US congress was 90% white. The actual number is 80% was white and 10% was other non-white. Black was 9%.
Oh yes, the Freedom Caucus, the most right wing Republican group in the house, is 99% white. There are 45 seats, so 99% means 44.5 members are white. More made up data.
No mention of the supreme court makeup. Then again Clarence Thomas is probably considered white.
Since 2017 the numbers for minorities have increased.