@jgweed,
Metaphysics is a very rewarding subject to learn. I am a fan of Aristotelian metaphysics myself. If you are interested in the "primacy of being" as he calls it, or really the origins of substance, you can pick up Aristotle's Metaphysics and just start in book Zeta, chapters 1 -10. Very interesting read. Other good metaphysics texts are Rene Descartes
Meditations on First Philosophy, Spinoza's
Ethic, Leibniz's
Discourse on Metaphyscis, Lockes
Essay Concerning Human understanding, Berkeley's
Principles ofHuman Knowledge, orHume's
Enquiry concerning human understanding. Take your pick. These are the standard texts for post modern philosophy on Metaphysics. You can read Kant for example, but even Kant draws references to these guys (rationalists and empiricists). Personally, Descartes is good, but very confusing to start with. I am much more of a fan of Spinoza? easier to read.
As to a good intro to philosophy book, I would recommend
20 questions: An introduction to Philosophy. I used that book in my senior seminar graduation course in university a while back. They give you core concepts in philosophy (more like questions) and they give you a few pages of supplemental material to get you acquainted with the subject and understand the abstract they give at the beginning of the chapter. If I was starting out in philosophy, I would pick up the book first. This is a link to amazon with the book on it.
Amazon.com: Twenty Questions: An Introduction to Philosophy: G. Lee Bowie, Meredith W. Michaels, Robert C. Solomon: Books
Though it is expensive, it is worth its weight in gold? well silver really. Beleive it or not, when I bought it it was $125!