IRVINE, Calif. — Bob Kelley, former publisher of the Kelley Blue Book — long considered the Bible of used-car valuation — has died at age 96, the Irvine-based company announced Monday.

“For a time, he was the most knowledgeable used car mind in the post-war United States,” Charlie Vogelheim, Kelley’s son-in-law and also a former Kelley Blue Book editor, said in a statement. “He’d drive home at night in the oldest car on the lot just to better understand why it hadn’t sold.”

According to the Orange County Register, Kelley died May 28 at his home in Indian Wells in Riverside County.

Robert Sidney Kelley began working for his family’s Southern California car dealership, which was founded in 1918, at age 15, according to the company. He left to serve in the Navy during World War II, then rejoined the business when he returned home.

Kelley’s uncle, Les, who founded the Kelley Car Company, would create lists of cars he wanted to buy and how much he wanted to pay for them. It was that list, which was initially only used internally, that grew into the Kelley Blue Book, which became the standard publication for car values.

Bob Kelley “took responsibility for appraising and reconditioning hundreds of used cars a month,” according to the company. “He pioneered the evaluation methods common across the auto industry today.”

The family sold the dealership in the 1960s, focusing its efforts on publishing the Blue Book, with Bob Kelley as publisher. The guide was released six times a year. According to the company, Kelley also led the guide’s expansion to the internet, with the website launching in 1995.

Bob Kelley retired in 2000.

“Bob Kelley was a true pioneer in the automotive industry,” Kelley Blue Book President Steve Lind said in a statement. “His legacy extends far beyond the pages of Kelley Blue Book. From its humble beginnings to the comprehensive online resource we know today, Bob’s impact has been immeasurable. As we honor Bob’s memory, we also recognize our responsibility to continue building on his legacy. Bob’s passion for informed decision-making will always guide us as we navigate the ever-evolving automotive landscape.”

Kelley is survived by Wanda, his wife of over 50 years; his sister; and his five children, 12 grandchildren and 10 great-grandchildren.