I recommend "Realms of the Human Unconscious: Observations from LSD Research" by Stanislav Grof (https://www.amazon.com/Realms-Human-Unconscious-Observations...) - he was one of the pioneers into psychedelic research, while it was easy and possible. For many aspects, it is... humbling. It seems that visions/senses/experiences of cosmic unity, or unspoken dread, or going beyond the physical world is more of a common theme of LSD.
However, I am torn, when it comes to its lack of skepticism. On one hand side, he hints that some aspects of extrasensory perception (e.g. clear visions of spermatozoid entering an ovum, visions of one's ancestors, etc) can be real, without noting some typical biases (e.g. people reporting coincidences only when they happen). Same, he seems to accept a lot of Freudian stuff uncritically. On the other, I am really happy he didn't censor the stories (or himself!) and share both processed and raw experiences. The overall narration is in the tone of a curious researcher knowing that he may get answers he is not looking for.
Overall, I recommend it a lot, keeping in mind that you don't take too religiously his mentions of Freud, Jung, birth matrices and extrasensory perception too literally. But... as a lens/perspective, that (though flawed/simplified) can yet be fertile.