Reddit mentions of Bonatti on Basic Astrology

Temples of the Sky is a really great, modern English source on the origins and significations of the twelve houses. This will get you started getting into the right mindset of how astronomical and planetary symbolism gets ingrained in other parts of astrology. It essentially gets your philosophical thinking cap started. There's also a section in the back that discusses various house systems and the things that are being emphasized (either space, time, a combination, or some external reference point) by their calculations to help you make a more informed decision about which house system to follow.

Traditional Astrology for Today I'm putting here sort of as an tangent thought, but this book does a good job of taking a step back and looking at the astrological philosophy and consultation from a historical context. You may find it interesting, maybe not.

Finally, there's Bonatti on Basic Astrology which is a really hard read, so get ready for that. But here Bonatti basically lays out the foundations of astrology and explains them as best as he can (with his crazy language). Difficult to access if you're not used to reading this kind of material, but filled with great information.

I'll send more things as I find them, working on some other projects atm.