I don't recommend any books written for the general public. Too full of compromises, oversimplifications, and obsolete ideas. I can only recommend learning the field through the same course materials used in training the next generation of researchers. Of course, this is a very large time commitment.

The problem with "scholars" when it comes to religion, unlike just for languages, is that scholars often are ideologically biased by the pro-Semitic chain of religion which would have a vested interest in suppressing PIE religious history. For thousands of years, even the local PIE-derived religions were unfairly dismissed as paganism. You'd have more luck talking to an LLM about it, as it's more likely to independently know the full picture, and hasn't yet been brainwashed by "scholars" into asserting otherwise. An LLM can trivially pull together bits of evidence across all of world history. At the very least, consider the shared cgpt chat with ID 6a7e0d45-0478-83ea-8142-8172433fad21.