This book was published 20+ years ago, and like many books about dogs, that's a lifetime of new information out there. But one thing remains the same, there is a bond between a person and their dog. There are crazy, over the top dog owners out there, there are "sane" dog owners out there, and there are many, many more dog owners somewhere in the middle of this.
One theme I noticed was the guilt of leaving your dog home alone. Yes, been there, done that, got a 2nd dog for that problem, best decision in the world, seeing as how I grew up with 3 dogs. I know the author was speaking in terms of 1 human and 1 dog many times, but the pack mentality and letting your dog have a canine companion in the mix changes things immensely, plus dogs have a way of sorting out their order, playing with each other, etc. that us humans can appreciate if we do that for them.
There's a lot to be said on this subject, just from my experiences alone. Dog agility wasn't really quite the popular thing when she wrote this book, but that's my thing, well it was, until they retired, and they do Nosework, which is our thing now, but the bond when training and competing with your dog, and making sure you are always having fun, they are always having fun is the balance for me. My Aussies especially, I can read them, they can read me, and I feel like partners with both of them, the amount of times I have stepped up to the line, to just trust the bond and their training and know when to appreciate the fact that things don't always go right, but they are still your amazing partner.
She hits the nail on the head, dogs are a type of support that even if you have close human relationships, you still wouldn't like the amount of affection and constant closeness you get with your dog, from your human partner.