This book was very good but would have been so much better if PN had waited until the end of Trump's term to put it together. It only covers his campaign and then his first two years of counterterrorism policy in office. It's very useful for those things, but obviously a lot of stuff (like the Soleimani assassination) happened in his second term.
This is my main criticism of the book, which is otherwise interesting, well-documented, and well-argued. Neumann's main arguments are 1. Trump did constitute a significant break from previous approaches to terrorism. Bush and Obama had significant differences, but they both tried to avoid demonizing Muslims, they didn't link terrorism and immigration as problems, they tried to stay within some boundaries of international law, and they believed the US had to make some effort to address the deeper causes of terrorism. Trump broke from all of these things, embracing autocratic allies, punitive violence, and Islamophobia. It was truly a view of the WoT that crawled out of the fever swamps of the radical right.
2. However, Trump was not fully able to enact this vision of the WoT because he was incompetent and rather indifferent toward staffing the federal bureaucracy and ensuring that his policies were enacted. He also wanted to devolve responsibility for fighting terrorism to "the generals" (people like SECDEF Mattis and the military leadership), and these figures wanted to keep the campaigns against terrorism within legal or ethical boundaries. This reality, of course, only fed Trump and the radical right's anger with the "deep state" and their desire to insert true loyalists and extremists if he wins the presidency again.
There's a lot packed into this book, including a good case that the chaos of Trump's policy-making and Islamophobic remarks actually harmed overall counterterrorism strategy and made the country less safe. Certainly his mainstreaming of white nationalist rhetoric, and his efforts to downplay right-wing extremism/terrorism, have had this effect. I just wish PN had waited for the end of Trump's term to do a full assessment.