Sonny, 77, was the editor-in-chief of Alfred A Knopf and chairman of the Knopf Doubleday Publishing Group.
People took to Twitter on Tuesday to express sadness and pray for his soul.
#SonnyMehta trended with 2,245 tweets.
Odisha Chief Minister Naveen Patnaik wrote on @Naveen_Odisha: "I am deeply grieved by the passing away of my brother-in-law Sonny Mehta (husband of my sister Gita Mehta). He was one of the world's best editors and an extremely civilized person. May his soul rest in peace."
Prime Minister Narendra Modi retweeted the post of the Odisha CM and wrote: "Sonny Mehta would be fondly remembered by countless avid readers across the world. He endeared himself to many thanks to his erudite and knowledgeable personality. Saddened by his demise. Condolences to Gita Ji, you, your family and his admirers. Om Shanti."
BJP leader Baijayant Jay Panda tweeted: "Deeply saddened at the passing of Ajay Singh "Sonnya Mehta, world famous publisher & wonderful human being. Condolences to his son, wife Gita, herself an accomplished author, brothers-in-law Prem & @Naveen_Odisha Patnaik, & families."
One tweet read: "The biggest kick is reading something new and exciting and then getting other people to share your enthusiasm. Beyond all the cant and hypocrisy in publishing, that's what it's all about. Sonny Mehta, publisher, RIP."
One user remarked: "Woke to the dreadful news that my friend and publisher Sonny Mehta died last night in New York. A unique and brilliant man. My thoughts are with his wife, Gita, and his son, Aditya, and with all his friends and colleagues at Alfred A. Knopf."
"This is such sad news. There aren't many giants in publishing, but Sonny Mehta was one. I wish his family and friends at Knopf all my sympathy. He was generous with his time and talent to authors, editors and agents, young and old and will be sorely missed," said another admirer.
( With inputs from IANS )