You mean the book goes into such great detail. The boy didn't write the book.
"The book was a complete game changer for me personally."
You should be more skeptical of claims without evidence.
The boy goes into great detail about what he saw when he was clinically dead about heaven and about what he saw both there and here. There is absolutely no way he would have known any of the details beforehand. I didn’t even know certain details, I had to look into the bible myself just to verify it.