I have not read the book, nor do I plan to. Please skip to the next answer if you don’t trust my uninformed opinion.
Still with me? Cool. This book speaks from a similar perspective to all other Western opinions on Buddhism. They want to treat a religion as a philosophy. Buddhism is not ‘mere’ philosophy. It’s an actual religion with millions of adherents. It has similar problems, traditions, cultures, dogmas, scriptures, and all of that. There is even violent politicized Buddhism, enough to support a Wikipedia page.
If you went to a Buddhist church / temple, the likes of which exist all over Asia, and talked to random parishioners, you’re not going to find a bunch of hardcore meditators. You will find exactly the same sorts of people and mindsets that you’d find in any Christian church in the US.
Religions serve a universal human need, the need to be safe and secure in the face of the terrifying uncertainty of the unknown and unknowable. Religions all over the world rhyme and riff off of the same concepts. The examination of those concepts is the study of theology, not the study of philosophy.
Why do Western Americans think differently of Buddhism? In short, the self-help industry, which has done a great job of packaging up Buddhist theology into something palatable for the Western mindset. It is these efforts that you’re idolizing when you proclaim Buddhism as the one true religion, a pastiche, not the actual religion.
Much is made of the Buddhist mystic tradition, but every other religion has it’s mystic offshoot. You have Christian mystics, Islamic mystics, Jewish mystics. If you study the broad strokes of these traditions, they’re all extremely similar. If you think about it, this shouldn’t be surprising. All attempts to directly explore the unknowable will inevitably involve some kind of meditation, and meditation is something anybody can do, and obviously there are patterns to it.
To say the Buddhist mystic tradition is any more right than the others is to make a horrifically naive mistake and tosses all rigor out the window. You have become exactly what you set out to avoid. Your distaste for the Christian framing of ultimate knowledge of reality has driven you to find a different framing.
When you become enlightened through following Buddhist dharma, you have converted to another religion, not done anything real. Christian monks obtain the same raptures, as do Sufis and Kabbalah students.
Own your spirituality, don’t let it own you. Buddhism has made important contributions to the realm of spirituality. But it isn’t any more ‘true’ than the others.