According to a New York Times Magazine article on the history of car-sharing, Brook came up with the idea for car-sharing while working as an energy-conservation agent for Oregon State University. He drew down his retirement account to launch the company's first four Dodge Neons in 1998.
By 2000, the company had $200,000 in annual revenue but was losing $50,000 per year. Brook and his wife, who had according to the Times article put $100,000 of their own money into the venture, sold the operation to Flexcar. Brook received what he described as "a token stake in the company." (He was not among the shareholders of 5 percent or more named in Zipcar's 2010 IPO filing.)
Brook then worked in what he described as "various responsibilities with them, including setting up their San Diego operation."
As of August 2010, he worked as an operations consultant for peer-to-peer carsharing company Relay Rides.