Goethe, Johann Wolfgang von "The Sorrows of Young Werther" (German: Die Leiden des jungen Werther) - 1774
This epistolary novel is also slightly autobiographical. Goethe has always been a very important German author. This is probably one of his most famous books very much to the disdain of the author.
Young Werther is a young artist, very sensitive. He corresponds with his friend whom he tells about all his troubles and sufferings, his unrequited love to a girl.
Apparently, the book had a huge influence on the people at the time. But not only contemporary readers were influenced, there are still German and international authors referring to the novel.
Thomas Mann wrote "Lotte in Weimar" where Goethe meets the young girl, Charlotte, Ulrich Plenzdorf, a GDR author, wrote "Die neuen Leiden des jungen W." (The New Sufferings of Young W.) in 1970 and it is still as actual as it was then.
From the back cover:
"Visiting an idyllic German village, Werther, a sensitive and romantic young man, meets and falls in love with sweet-natured Lotte. Although he realizes that Lotte is to marry Albert, he is unable to subdue his passion for her, and his infatuation torments him to the point of absolute despair. The first great 'confessional' novel, The Sorrows of Young Werther draws both on Goethe's own unrequited love for Charlotte Buff and on the death of his friend Karl Wilhelm Jerusalem. The book was an immediate success, and a cult rapidly grew up around it, resulting in numerous imitations as well as violent criticism and even suppression on the grounds of its apparent recommendation of suicide. Goethe's sensitive exploration of the mind of a young artist at odds with society and ill-equipped to cope with life is now considered the first great tragic novel of European literature."
I also read "Iphigenia in Tauris".