This is the first Whitehead I have read. I found it to be stimulating and psychoactive, it's somewhat dense but still quite readable, based on a series of his later lectures.

I learned about the challenge of using language to describe the most basic parts of our experience, as language tends to focus on those things that change and might therefore need communicating. I learned about ontologies that include interior experience as primary things, i.e. "the sense of importance" as a fundamental part of reality. I learned about his attempts to have an ontology that more closely matches the then-new breakthroughs in the new physics, and how he tends towards the relational, with "occasions of experience" being at the core of things.