If you ever heard of Spinoza, you have probably heard also of his "Ethics". This book is simply Spinoza's finest and most valuable book. One could say many things about the "Ethics", but they would be unnecessary: if you want to know about the book, buy a guide or read a compendium on the history of philosophy.

But this is the actual text; here there is no talking about the book, only the actual getting inside it.
The "Ethics" were first published in 1677, in the "Opera Postuma", right after Spinoza's death. The first reaction to it was of disgust; later on, with the german idealists, Spinoza was recuperated from a mistreatment, and was even considered to be the true beginning of all good Philosophy (Hegel). In the end of the 19th century, Elwes published the "Ethics" in the english language for the first time; in the 20th century, 2 new translations appeared, the one by Samuel Shirley, and this one, by Edwin Curley. Edwin Curley, actually, decided to publish, in the 1980s, the collected revised works of Spinoza in english, where in the first volume was included his translation of the "Ethics". This is the translation included in this Penguin volume.

Edwin Curley is a reputated scholar on Spinoza and his translation of the "Ethics" surpasses any other ever written in the english language: it is the most quoted and consulted translation of the "Ethics" by the english-speaking scholars, and it well deserves its success.

If you want to read Spinoza's "Ethics", this is your edition.