I know several people who happily adopted older dogs. One was my neighbor who adopted a 7-year-old mixed breed, her first dog. Chance led a happy, healthy life for 11 more years! Another adopted two Swedish Valhunds at 9 years of age. The two walk miles each day and still compete in agility trials.
My two Havanese are now 7 and 11 years old. I never really actively trained them very much beyond "sit", and was curious about "teaching old dogs new tricks." So I decided to try out some sit-stay-come stuff and was amazed how quickly they caught on and how well they retain it. Even Riley, the 11-year-old. I'm thinking of enrolling them in a class--just for fun.
McConnell is also the author of a number of other books, including "The Other End of the Leash," which I own, read and love.