Spinoza's conception of "God" is far too sophisticated to describe simply as "pantheist." His definition of God resembles that of the Scholastic tradition — God is that without which nothing could be, nor could be conceived (thought of). For Spinoza, this metaphysical primary has no innate thought or person, and is similar in this respect to Ain Soph, a concept to which, as a young Jew and promising scholar of the early 17th Century, could hardly have avoided exposure. Unlike the Ain Soph of the qabbalah, which Spinoza thought was an abortive and arbitrary method of hermeneutics and scriptural interpretation, Spinoza's God isn't really transcendent except insofar as He (or She when referred to as Nature) is beyond our limited capacity to understand all in one gulp. On the other hand, like the God of William Blake's early works, Spinoza's God acts and is through existing men; ie., we are God in our essences. Our essence, Spinoza tells us, is virtue or power — the two being synonymous for him, because our preservation is the preservation of the cognitive capacity of God.
In Ethica ordine geometrico demonstrata ("Ethics geometrically demonstrated"), Spinoza's main concern is suffering. Spinoza wanted to show a way of resolving suffering into a blessed condition,* rather than merely aggravating it with misguided Stoicism. As man only acts from desire, and only to realize pleasure (in the philosophical sense; "joy") or avoid pain ("sorrow"), the only "out" is to find some source of joy which can never be taken away, which is always readily accessible, and which provides a new perspective for dealing with any conceivable trouble that one might encounter.
This joy, Spinoza tells us, is love for God. It's worth noting, however, that this "love" isn't like a Jew or Christian's love for Jehova. On the contrary, because God is not a personal god, "love of God" actually more accurately corresponds to Nietzsche's celebration of amor fati — the unconditional love of Fate, the blind turnings of the universe by which all things, both the fortune we acquire and the pains we can't avoid, are all possible and necessitated. As Borges called it: "El amor que no espera ser amado" – love with no hope of being loved.
There are several fascinating themes lurking under the surface of Spinoza's pristine and meticulous exposition. One is that the highest good and natural right is self-interest, and that an identification of evil reflects inadequate knowledge of the working of fate, as well as a weakness, the inability to turn a liability into a strength. Indeed, the only real link between Spinoza's worldview and the worldview of the Christian Renaissance prevailing at the time, was Spinoza's rather dubious use of the word "God" to describe the blind and impersonal turnings of the cosmos.
It is our supreme fortune that Spinoza lived in a republic which respected freedom of speech.
*"Blessed" is, by the way, the meaning of his given name, Baruch, and the latinized version ("Benedictus") he adopted upon excommunication from his synagogue, though both of these are different from the actual word he used for "blessedness" in his Ethics (beatitudo).