The author recounts both his own experience in search of old roses -- roses whose varieties predate the Hybrid Tea rose, which has taken over so thoroughly -- and various chapters of the history of the rose. A far from complete history, but it has some interesting part.
The rediscovery of the true musk rose -- which, BTW, blooms in the fall, not the summer.
The development of cemeteries, and how roses were planted on graves. People looking for old roses often check out old cemeteries, and take samples from the bushes they find there. Identifying them can be -- quite interesting.
Roses in ancient Rome, where a farmer could do quite well with "coronary flowers" -- flowers used to make crowns at banquets. Roses were one of the best, and they prized them most for the smell -- unlike modern roses!
How an archaeologist found the oldest roses known to be used in a funeral ceremony -- ancient Egyptian. Recognizably a rose still in use for that purpose.
How Empress Josephine took to horticulture as Napoleon got bored with her, and part of that was the roses. (They get mentioned in her obituary.) She collected as many strains as she could which had a big impact on European rose breeding. Particularly since her husband brought back yellow roses from the Middle East. Most strains of yellow roses are descended from those yellow roes.
Roses from China. The Tea roses were brought by the tea trade -- but they were called "tea" because they smelled of tea. (The author had actually smelled one of the original, authentic rose and says -- Oolong.) Many of which were taken out with the same tact and sensitivity as they got their hands on tea and silkworms. And they were, of course, renamed by their "discoverers."
Roses in California. The gold rush territory is a mother lode of old roses. Carefully brought by the women and cherished there. The first man to collect them was able to actually speak to the settlers who planted them in some cases. Nowadays, there is much more fun in figuring out what they are.
My rose experience is limited to checking out the local rose garden in the public park -- some years. It was still a fascinating book, full of stuff.