“That’s fine, but I’ve been reading religious books since I was in grade school.”
I too, was in that position. What it took for me, was to quit reading about it, and start writing my own ‘living’ book. Years ago I cried out to God, calling upon Him and as many of the people I had read about, with all my might. That was on the beach in Texas. The following morning my cries were answered as a man approached me (whom I had never met before) and introduced himself. He told me that I had cried out. He invited me to a place up in the redwoods just off the coast, where I spent the next 3 1/2 months in prayer and meditation, living in a gutted out airstream, and barely eating. During those 3 1/2 months, God answered me and showed me many of the things Dr Alexander describes in his book. Can I give you concrete evidence of those things? No one can but He who created us, and All.
God is faithful and true. He will answer you, but you have to ask, and really want it. The book is accurate, and affirmed, at least for me, what had been revealed to me. There is nothing new under the sun.
A consistent theme of a lot of these is that much of the specifics match cultural and geographical variances of faith. For instance, Muslims tend to feel the presence of Allah and meet Muhammad when they have NDEs. Christians see Jesus and/or the Abrahamic God. Hindus meet Vishnu, children meet Santa.
This makes sense if these are functions of the brain. The constant is the transcendent and numinous experience that people can have, not the various gods they ascribe them to. I don't doubt that you had an experience (or Dr. Alexander), but it doesn't prove religion true.