The 36-year-old third baseman was activated off the disabled list.
"It's good to be in this position and back here after all that has gone through in my life this year. I'm excited about it," he said.
Boone was not in Tuesday night's lineup against the Chicago Cubs, but will play soon, manager Cecil Cooper said.
"He can pinch-hit, play tomorrow, there are a lot of options. I want to do it as soon as I can. I don't want to wait too long, cut the suspense. I know he's pretty anxious and everyone wants to see him out there," Cooper said.
Boone signed with the Astros in the offseason, then had an operation on March 26 because of a congenital defect in his aortic valve. He has already completed a minor league rehab assignment.
At the time of his surgery, the 11-year veteran did not expect such a speedy return.
"Five months ago, no," Boone said. "But I think fairly shortly after surgery and once I knew everything went well, I wouldn't say it was a priority, but I certainly thought it was possible."
Boone said he was impressed how much the Astros organization supported him through his rehab.
"Unbelievable. I've been blown away by how much they have been behind me, how much they supported me, how much they made this completely about me, I feel forever grateful to them by the way they have treated me," Boone said.
Boone has played for Cincinnati, the Yankees, Cleveland, Florida and Washington, batting .264 with 126 homers and 555 RBIs.
"It's just remarkable that's he's come this far. I didn't think he was going to be able to play this year. My thoughts was for him just to get healthy and live a normal life," Cooper said. "He's got some will and determination to get all the way back."