In my attempt to eventually finish reading all things Kafka, I read the first volume of his predictably strange but often fascinating two-volume diary collection, The Diaries of Franz Kafka: 1910-1913. Never meant for publication, these diary entries are raw, unpolished, quite personal, and often deeply insightful in terms of Kafka’s literary ruminations. The diaries include rough drafts for stories, descriptions of very strange dreams, plot summaries and criticism of Yiddish plays, criticism of Yiddish actors and performers, reflections on books, details on daily life, food and dress, descriptions of acquaintances and socialites from Prague, self-deprecating passages in which Kafka doubts what he believes is his limited talent, reflections on the importance of literature and writing in his life, morbid fantasies of suffering and dying, guilt-ridden passages describing how little Kafka has written, and reflections on young and married women with whom Kafka was clearly interested.
For anyone interested in Kafka, probably Metamorphosis, “The Doorkeeper’s Parable,” and “A Hunger Artist” are the best places to start. I would follow those with The Castle, “The Judgment,” “In the Penal Colony,” and The Trial. But if you want to dig a little deeper into what kind of person Kafka is and how his life clearly shaped his stories, the diaries are where you’ll find the so-called inner Kafka, the man behind the stories. He had a conflicted relationship with his father and mother, a sometimes jealous and overly critical relationship with his friend Max Brod (who would become Kafka’s literary executer), a deep interest at least for part of his life in the Jewish theater, a vivid imagination, and a darkly wry sense of humor. On the whole, I suppose reading the diaries makes him seem a bit more “normal” than one would gather simply from reading his stories. The play summaries and criticism, reflections of novels, and his interest in women are aspects that most people (or most writers) would record in their diaries. But then you get these brief descriptions of very dark and pretty disturbing passages. One motif he continually comes back to is the image of Kafka lying down with someone or something sitting or pressing down on him, making it impossible for him to get up. In one reflection, he imagines himself pulled up through the ceilings of several apartments until his skin has been shorn off of his body and his skeletal remains crash through the roof.
You can read some of the diaries here. They are also published in book form.