The winner, who will receive a £50,000 prize, is set to be announced at a ceremony in London on Monday.
Miller is currently favoured at 15/8 odds for his novel The Land in Winter, while Desai is a close second at 2/1 for The Loneliness of Sonia and Sunny.
A win for Desai would mark her second Booker Prize, placing her among only five authors to achieve this double victory.
The shortlist also features David Szalay, Susan Choi, Katie Kitamura, and Ben Markovits, with judges highlighting the books' exploration of significant issues such as migration and class.