I've only read one other Robert Sawyer book (Illegal Alien), and didn't care for it much. But I saw this at a discount store, and the concept looked interesting. I'm glad I picked it up.
Much of the book is crowded with pop culture references. Since the book hops between two time periods, I presume these were mainly intended to provide a sense of period, but their main effect was to make the book seem dated - despite being only a few years old. While most of the in jokes were carefully explained, they also weren't very interesting. This despite a lead character from my own generation.
The story contains some gaping realism holes in characterization - especially regarding the billionaire philanthropist - and they did obtrude into my suspension of disbelief. The actual plot, however, was fairly sound. The tension created by the lopsided rejuvenation was decently explored, and there were several really touching moments. Not all of it worked that well, and Sawyer could have done more with the lead couple's relationship, but overall, it worked nicely.
The ending felt a bit rushed and wishful, and I thought Sawyer missed some pretty obvious openings for a more moving note that wouldn't have affected the basic tone. Generally, though, this was a nice novel in which the science was, if not incidental to the relationships, at least sharing the billing.