meaning - Can you paraphrase the highlighted part of passage please?

Writing to the woman who would become his third wife, Hermann Hesse complained: “Life for me now holds almost no pleasures any more, in fact I am living in Hell.” The event that had reduced Hesse to this state of near-despair was that his wife-to-be Ninon Dolbin had moved some of his books without his permission. For him this was an intolerable disruption of the orderly existence he believed essential to a writer who had detached himself from the world. His independence required that he hold all of humankind, and even his closest companion, at a rigorously policed distance. Accordingly, although the two of them lived under the same roof, he communicated with Ninon mainly in writing. As his latest biographer, Gunnar Decker, relates: Their day-to-day communication with one another was conducted by “house letters”, like in a Trappist monastery, where one has to stay silent most of the time and jot down essential communications to one’s fellow monks on pieces of paper. This was the way Hesse managed to tolerate the presence of another person in his vicinity; he had to be sure he wouldn’t suddenly be spoken to. “How was it,” Decker asks, “that Hesse believed himself to be ‘living in Hell’…when he had a female friend who loved him more unreservedly than any before her, and who placed herself entirely at the service of his needs?” As he comments: “His note sounds positively hysterical.” It is a reasonable judgement. Decker is a scrupulous biographer with an unrivalled knowledge of his subject, and this is undoubtedly the definitive account of Hesse’s life and work. It is less clear what Decker finds of intrinsic interest or value in his subject. The most striking fact about Hesse is how he was embraced by the counterculture in the early Sixties – a development that secured him a posthumous reputation as an exponent of the hippie “drop out” philosophy and made him the most widely translated 20th-century German author.

• I need to translate this passage into a different language. Can you paraphrase the highlighted part please? My interpretation is : Decker was kind of biographer who pays attention to detail and had a great knowledge of his subject (Hesse) and his work regarding Hesse is the ultimate work a biographer can do on Hesse life, and this is a clear fact, but it is less clear to us ( audience of Decker) what values he found in Hesse.