The last book I read by Robert Sawyer dealt with the issue of near immortality by uploading a "copy" of the human mind to a mechanical body. This time around, he elects to tell us of another method of life extension, which he call's a "rollback", also the title of the book.
A rollback is an assortment of procedures that uses gene therapy, nano-robotic drones, cloning organs, and traditional surgery to essentially turn back the living clock that we are counting down to. The clock can be set back as early as the age of 25.
Although the process is extraordinarily expensive (not even multi-millionaire celebrities and sports icons can afford this luxury) Sarah and Don Halifax are given the procedure because a certain party thinks Sarah Halifax should be present for their ongoing commucations from an Alien species know as the Dracons, whose home is almost 19 light years away.
Although Sarah's husband, Don, isn't particularly needed for the Alien communications, Sarah wouldn't even consider the possibility unless her husband would be granted a rollback, as well.
When the rollback procedure is complete and the effects seen to be recognizable (a couple of months after the procedure is finished) Don, is reaping the benefits of youthfulness and vigor. However, Sarah's body had some interfering factors (a result of treatment for a previous cancer) that inhibited the success of the rollback.
Not the least resentful, Sarah is in a race to decode the latest message from the Dracons, before her weary body succumbs to the aging process, while Don struggles to adapt to his new found youth and vitality.
Sawyer succeeds in portraying how such a rollback affects the inquiry of immortality and the disadvantages and struggles it could assume, as well.
Contrasting the difference in physical age between Sarah and Don, he also shows us that true love and respect knows no such boundaries.