Andi ...
I simply love Jack Harkness as a rose author. Some of his rose growing advice is dated and certainly slanted towards the European climate, but he has a wonderful sense of humor and I've always liked his priorities. OK .. here's another one of my favorite quotes. He ended his book Growing Roses with:
".... I have a horror of the modern monomania, the idea that one becomes absorbed in one thing for its own sake. However absorbing, any one interest is a part of life, not the whole of it; an addition to life, not a subtistitute for it. Roses, like all good things in this world, are fit company for laughter, and good fellowship; enrichers of a full life, multipliers of the happiness of the human race; a golden part of life, but not life's whole."
He was writing about roses, but he could have been writing about all of gardening.
One of my favorite rose books that he has written, which is less technical is Makers of Heavenly Roses because he talks about the breeders of roses and it kind of gives you a time line of the development of roses through the various classes to the modern roses of his time ... mid 20th century. Good reading.