Shelley began writing fiction late in life, publishing his first novel
The Shrimp People in 1991 at the age of sixty one. The first substantial novel by a Singaporean writer about the Eurasian community in Singapore, it was the best-selling local paperback at the Times bookshop for three consecutive weeks between 22 August and 5 September 1991, and remained in the top five until 11 December that year. The work won the National Book Development Council of Singapore Award for works in English the following year despite being up against books by established writers such as Gopal Baratham and Suchen Christine Lim. He wrote three more books,
People of the Pear Tree (1993),
Island in the Centre (1995) and
A River of Roses (1998), on the same theme within a decade. The first two of these won National Book Development Council Highly Commended Awards in 1994 and 1996 respectively, while the last won the Dymocks Singapore Literature Prize (now known simply as the Singapore Literature Prize) in 2000.
According to poet Edwin Thumboo, an emeritus professor of the National University of Singapore, Shelley "was a sensitive and acute observer of life. Because he started writing late, the material that generated his fiction was well digested. He brought to bear on it all the insights of an engineer, businessman, administrator, public servant and a person who loved life. His character analysis was therefore penetrating, and his range of characters are fully reflective of the society he wrote about." Associate Professor Kirpal Singh of the Singapore Management University, himself a writer and literary editor, has commented that although Shelley's impact on the Singapore literary scene had been "much less than it ought to be", his body of work was significant for both the Eurasian community and the wider Singapore society:
Rex belongs to the small but significant group of writers who have articulated the experiences of the Eurasians. I think, some over-writing notwithstanding, Rex's contribution is admirable. At its best, Rex's writing is passionate, humane and highly focused. Though he generally kept a low profile, his literary works will stand the test of time, combining a sharp sense of observed commentary with historical detail.
Shelley was the 2007 Singaporean winner of the S.E.A. Write Award. In August 2009, Marshall Cavendish, a subsidiary of the Times Publishing Group, reissued Shelley's books
The Shrimp People and a non-fiction work first published in 1995,
Sounds and Sins of Singlish.