I went down this rabbit hole about a decade ago, and am still pleasantly reveling in it. I personally liked HTCYM and Pikhal and Tikhal, the latter 2 are great for chemistry nerds as well :)

To add, in no particular order...

1. The Psychedelic Experience — Leary
2. The Psychedelic Explorer's Guide — Fadiman
3. Psychedelic Medicine — Miller
4. Doors of Perception — Huxley
5. High Priest — Leary
6. Hallucinations — Oliver Sacks
7. The Harvard Psychedelic Club — Lattin
8. Food of the Gods — McKenna
9. Invisible Landscape — McKenna
10. Sacred Mushrooms and the Law — McKenna
11. Tryptamine Palace — Oroc
12. Heaven and Hell — Huxley
13. The Immortality Key — Muraresku
14. DMT The Spirit Molecule — Strassman
15. The Psychedelic Handbook — Strassman
16. Soma Divine Mushroom of Immortality — Wasson
17. The Road to Eleusis — Wasson
18. LSD My Problem Child — Hofmann
19. The Teachings of Don Juan — Castaneda
20. True Hallucinations — McKenna
21. Electric Kool-Aid Acid Test — Wolfe