Chen had interviewed 183 people by 1984 and decided it was time to start writing.

Xu passed away the following year, and the book was published in 1987.

It sold thousands of copies within a few days.

Chen went on to release a series of three books on Xu in 1989 that sold millions of copies.

"I was encouraged," Chen says.

"I knew biographies would sell since novels were difficult to publish. But I didn't expect they'd be so popular."

In 1991, a publishing house in Shandong province's Qingdao bought the copyrights of the books Chen would write in the next decade, making him the country's first author to secure such a contract.

Two years later, his biography of Soong Mei-ling was reprinted almost 10 times within a year of its release.

Seven of Chen's 108 books are about environmental protection, while the others are biographies.

China Society Press recently republished a collection of his 14 most popular works.