Orbit by John J. Nance
Nance is known for aviation fiction, this excursion into near future SF is atypical for him.
The premise is a private firm, American Space Adventures, doing commercial low-orbit flights for wealthy enthusiasts. A jumbo jet takes a small spacecraft up to 60,000 feet and releases it. The spacecraft then uses rockets to get up to 250 miles. The passengers get to enjoy four orbits around the Earth and are back on the ground within a few hours. On many flights, there are 3 paying passengers ($500,000 each), plus one passenger who won a contest to be on the flight. In this story, Kip Dawson is the contest winner and all three of the other passengers become unable to go. However, the flight is also being paid to take equipment into orbit, so the firm decides to go ahead. Kip's wife is afraid something will go wrong and insists he not go. This leads to her leaving him. There are also issues between Kip and his grown son from a previous marriage.
Almost as soon as the craft reaches orbit level, a small piece of space junk shoots through the craft. The craft's hull manages to re-seal itself. However, the pilot has been killed, communications with Earth have been severed and there's a problem getting the rockets to fire. The craft can only provide Kip with several days of breathable air. Kip was given a crash course about the spacecraft before being allowed to fly in it. And there is a binder full of "how to do it" lists onboard. But he’s not an astronaut.
Meanwhile, there's intrigue on Earth with a NASA director who doesn't want to do a rescue mission (as a result of hostility towards the private company's leader). And he’s willing to undermine efforts by others to send help. Russia attempts to send a rescue mission...
Partly as a means by which he may be able to leave messages for his family that could be found after his death, Kip begins to write his thoughts in a document on a notebook computer. It turns into an extensive journal - reminiscing about his youth, re-thinking what happened to his marriage, discussing life in general... Unknown to Kip (and overlooked by NASA), there is a one-way communication link that's still working - putting his ongoing journal on a server on Earth. After a hacker stumbles upon it, following Kip's writing becomes a fascination of people around the world.
The book is more of a very-near-future disaster story than what many readers may associate with "science fiction". Like many near-future stories, there are no real issues of scientific plausibility. Readers who have been following real world news of private companies trying to establish sub-orbital or low-orbit flights may be interested in a novel on the topic. Other SF readers who are more inclined to stories further in the future may find less to be awed by in Orbit.