^ that website is the most expansive resource that I go to right now.
What got me into Alchemy at all was Catherine MacCoun's On Becoming an Alchemist which explained Hermeticism very well but took more of a psychological and emotional approach to it.
"The Mirror of Alchemy" by Roger Bacon is a short, comprehensive text, although I guess like a lot of alchemical texts, there's a super super super secret ingredient that the writer of the alchemy book only says that they can't say. And that's what makes the Philosopher's Stone, along with all the boiling and pressure-cooking. It's supposed to congeal into a red stone or something.