Part of me likes to plunge bald-headed into the works of philosophers, sink, rise, sink and rise with at last some un-mediated understanding of my own but to be truthful with a complex thinker like Santayana who has a lingo of his own a little introductory reading can avoid a striated poll. What can he mean by matter as metaphor? What's an essence anyway? Is it Platonic, Aristotelian or a simple of his own? A quick reading of the entry on him by Matthew Caleb Flamm in the Internet Encyclopedia of Philosophy will prepare you for a smoother reading that still leaves your judgement un-coerced by the heavy hand of an expert. I often find that the I.E.P.will do that. The cynic in me 'suspects' that the Stanford E.P.may be the first and last recourse of the student who is more concerned with academic achievement than reading the text. Am I right or am I right? It's not realistic to read everything and only an unambitious fool would read all of Kant's Critique of Pure Reason as a student. I can't say that reading dented my perplexity in any quantifiable way but it was honest if stupid. I must read it again sometime.
A via media is the book of readings or extracts from the major works. I have a modern libraryThe Philosophy of Santayana ed. Irwin Edman which gives a panoptic view which I got for a mere €4. It has for instance an extract from Reason in Religion - How Religion may be an Embodiment of Reason and straight after it but not Literally True. He means not actually true of course. It may be metaphorically true like Science. George talking dirty.
Now read on.