As a student, in an hour when he was needing the help of sages, he followed Renan; Spinoza freed his mind in matters of religion; from afar came the … - Benedictus de Spinoza

Sed amor erga rem aeternam et infinitam sola laetitia pascit animum, ipsaque omnis tristitiae est expers; quod valde est desiderandum totisque viribus quaerendum.

Speaking of Spinoza he [Nietzsche] says: "How much of personal timidity and vulnerability does this masquerade of a sickly recluse betray!" Exactly the same may be said of him, with the less reluctance since he has not hesitated to say it of Spinoza. It is obvious that in his day-dreams he is a warrior, not a professor; all the men he admires were military.

The Ethics is a book of concepts (the second kind of knowledge), but also of affects (the first kind) and percepts (the third kind) too. Thus the paradox in Spinoza is that he's the most philosophical of philosophers, the purest in some sense, but also the one who more than any other addresses non-philosophers and calls forth the most intense non-philosophical understanding. That is why absolutely anyone can read Spinoza, and be very moved, or see things quite differently afterward, even if they can hardly understand Spinoza's concepts. Conversely, a historian of philosophy who understands only Spinoza's concepts doesn't fully understand him.