"Fear and Loathing" was No. 15 on Amazon.com as of Wednesday and publisher Vintage Books has ordered a "significant" reprinting.
"We usually sell about 60,000-70,000 copies a year of that book and our next printing will be close to that total," Vintage spokesman Russell Perreault said.
Other Thompson books selling well include "Hell's Angels," "Fear and Loathing: On the Campaign Trail '72" and "Hey Rube."
On Wednesday, a family spokesman said Thompson did not take his life "in a moment of haste or anger or despondency" and probably planned his suicide well in advance because of his declining health.
Douglas Brinkley, a historian and author who edited some of Thompson's work, said the founder of "gonzo" journalism shot himself Sunday night after weeks of pain from a host of physical problems that included a broken leg and a hip replacement.
"I think he made a conscious decision that he had an incredible run of 67 years, lived the way he wanted to, and wasn't going to suffer the indignities of old age," Brinkley said in a telephone interview from Aspen. "He was not going to let anybody dictate how he was going to die."
Thompson spent an intimate weekend with his family, the spokesman said. His son, Juan, daughter-in-law, Jennifer, and young grandson, William, were visiting from Denver.
"He was trying to really bond and be close to the family" before his suicide, Brinkley said. "This was not just an act of irrationality. It was a very pre-planned act."
Family members had no hint that Thompson planned to take his own life, Brinkley said, and he did not leave a note. "There was no farewell salutation," he said.
Brinkley said Thompson's son and grandson were the only other people in the home at the time of the shooting. Juan Thompson said he heard a noise that sounded like a book hitting the floor, ran to the kitchen and found his father dead, Brinkley said.
Thompson's wife of two years, Anita, was at a health club.
The family is looking into whether Thompson's cremated remains can be blasted out of a cannon, a wish the gun-loving writer often expressed, Brinkley said.
"The optimal, best-case scenario is the ashes will be shot out of a cannon," he said.
Other arrangements were pending.