
"This new edition of Samuel Shirley's translation of the Theological-Political Treatise - a revision of that published by E. J. Brill in 1991, based on Gebhart's Heidelberg edition of 1925 - is accompanied by a new Introduction and Notes prepared especially for this volume by Seymour Feldman. Included also are Spinoza's supplementary notes, and an index of Biblical references."--BOOK JACKET.
The deepest and most interesting philosophical books are generally difficult and best accompanied by some form of instruction. This is true regardless of how clearly (e.g. Plato) or esoterically (e.g. Kant) written they are. There are some good secondary sources that can help but it's far preferable to be able to talk to an expert in a one-on-one or smallish setting. It would take a long time to explain why this is the case, so I'll just leave it as an assertion here.
Okay, that being said, I wouldn't want to dissuade anyone from reading philosophy on their own. Here are some recommendations for books and articles that can be (more) fruitfully read on one's own. Anything marked with a + is a secondary source. Ideally I'd be giving you excerpts from each of these in a reader for a course. I'm going to skip some people like Aristotle who should be approached in carefully selected excerpts or with a guide, and also some more obvious things that almost everyone with a college education has read, like Descartes' Meditations or Plato's Republic.
On Fate, Alexander of Aphrodisias
+ Problems from Locke, Mackie
Tractatus Theologico-Politicus, Spinoza
+ The Courtier and the Heretic, Stewart (on Spinoza and Leibniz)
Enquiry Concerning Human Understanding, Hume
Groundwork of the Metaphysics of Morals, Kant
Prolegomena to Any Future Metaphysics, Kant
On Liberty, Mill
"Modern Moral Philosophy", Anscombe
"What is Capitalism?", Rand
The Bounds of Sense, Strawson
+ "Rawls on Justice", Nagel
"The Naturalists Return", Kitcher
Sources of Normativity, Korsgaard
This crowd in particular might be interested in some of Frege's work as well, e.g. "What is a Function?" and "Sense and Reference."
Unfortunately it seems Wittgenstein didn't understand (or chose to reject) the second half of the treatise he borrowed from (which very roughly is "given this model of the world/ethics, a model of emotion, and a model of emotion as a function of the world/ethics, what doesn't it make sense to feel?"), and didn't live a happy life.
