A. Wolf 
The Correspondence of Spinoza [PDF ebook] 

First published in 1928, The Correspondence of Spinoza is deeply interesting in many ways. It presents a pageant of the leading types of seventeenth-century mentality. It affords contemporary glimpses of important scientific researches and discoveries. It brings us into touch with some of the social and political events and tendencies of the period. This book includes correspondent letters containing things of first-rate importance for the correct interpretation of the philosophy of Spinoza.