These days, the main criticism of Haruki Murakami is that he’s spent most of his career writing the same story over and over. To a certain extent it’s a fair point: cats, jazz, spaghetti and questionable female characters will all make an appearance at some point; but rather than making jokes, it’s interesting to ask why. Some put it down to age, some to the author resting on his laurels, others to a desperation for that elusive Nobel Prize. Yet clues can be found in his own writing, specifically “Underground.”

Underground: The Tokyo Gas Attack and the Japanese Psyche, by Haruki Murakami Translated by Alfred Birnbaum and Philip Gabriel.

384 pages

VINTAGE INTERNATIONAL, Nonfiction.

March 2020 is the 25th anniversary of the Tokyo gas attack. On the morning of March 20, 1995, followers of the Aum Shinrikyo cult unleashed sarin gas in the packed Tokyo subway. Twelve people died, thousands became physical and emotional casualties. A tangential — and far less important — result of the attack is that Murakami’s writing changed forever. This is the story he is endlessly telling, like a modern-day manifestation of Coleridge’s “The Rime of the Ancient Mariner.”

It’s worth taking a look at where “Underground” comes in Murakami’s chronology. He published “Hard-Boiled Wonderland and the End of the World” in 1985 and left Japan for — what he calls in “Underground” — “self-imposed exile” a year later. “Norwegian Wood” came out in 1987 and made him a star. While away, he wrote what is widely regarded as his masterpiece, “The Wind-Up Bird Chronicle.”

He knew, by his own admission, that he’d reached a watershed in his writing. Artists who achieve a perfect manifestation of something they’ve been working toward tend to feel emptiness in consummation and start looking around for something new. He wanted to “go back (to Japan) and do one solid work, something other than a novel, to probe deep into the heart of my estranged country. And in that way, I might reinvent a new stance for myself, a new vantage point.” “Underground,” the work that resulted from this new ambition, was published in two parts, in 1997 and 1998, and translated into English in 2000.

In the 20 years that have passed since then, it remains an outlier in his oeuvre, and a springboard for the career that would follow. He started “probing” then and every story since then has been, in some way, a continuation. This is most obvious with “1Q84,” which features an Aum-like cult, but a preface for every book since 1995 can be found in the pages of “Underground.”

Murakami has published many nonfiction books, but so far only three have made it into translation in English. I know from personal experience of trying to get translation rights that he won’t even contemplate allowing the translation and publication of some of them. He is a writer who retains very careful control of his public reputation, especially outside Japan. In 2015, he had his first two novels retranslated into English and suppressed the originals because he wasn’t happy with them. Viewed in that light, that he chose “Underground” as one of the only nonfction books to be published in English is telling.

It is a keystone in the Murakami canon, the book that explains every other book, the Rosetta Stone for latter-day Murakami literary criticism.

Read archived reviews of Japanese classics at jtimes.jp/essential.