Reddit mentions of The Essential Spinoza: Ethics and Related Writings (Hackett Classics)

It's not clear at all what you're asking for. If you are looking for a way to get into Spinoza, the first place to start is to read his Ethics. Alongside you can read articles about him on the SEP, IEP, and Wikipedia.

The Ethics is written like a geometry treaty (as opposed to Descartes' Meditations which are written as a form of meditation, quest for knowledge). Spinoza wrote logical arguments. There are propositions, and for each of them there will be proofs and corollaries. What you need to understand is the structure and division of the book. Once you know what each section is about, you will have a better time mapping the arguments together.

In regards to Descartes, Spinoza is an amazing contrast because he offers an altruistic view rather than an egoistic one. The major rationalist philosophers (Descartes and Leibniz especially) have an egoistic philosophy: everything starts from the ego, the I, and everything is supposed to be a first person perspective basically (I'm grossly summarizing). Spinoza goes in a different direction by offering a view that is altruistic. In the Part IV of the Ethics you'll find his argumentation for a view that goes beyond the simple perspective of the ego. In fact Spinoza barely cares about the ego in my opinion. He thinks that the ultimate goal is to achieve total understanding of God (and God is a tricky term since for him it can mean Nature, or the universe overall, the totality that encompasses all ways of being), and he thinks this can be done collectively rather than individually. Spinoza is a monist: he thinks there is only one substance (which he calls God) and everything else is derived from it (modes of being).

The best edition I recommend is this one: https://www.amazon.com/Essential-Spinoza-Related-Writings-Classics/dp/0872208036

It contains the Ethics and other writings. The introduction from the editor is great as well.