In 1903, despite the vehement objections of his parents, Albert Einstein married Mileva Maric, the companion, colleague and confidante whose influence on his most creative years has given rise to much speculation. Beginning in 1897, after Einstein and Maric met as students at the Swiss Federal Polytechnic, and ending shortly after their marriage, these 54 love letters offer a rare glimpse into Einstein's relationship with his first wife while shedding light on his intellectual development in the period before the annus mirabilis of 1905. Unlike the picture of Einstein as the lone, isolated thinker of Princeton, he appears here both as the burgeoning enfant terrible of science and as an amorous young man beset, along with his fiancee, by financial and personal struggles - among them the illegitimate birth of their daughter, whose existence is known only by these letters.