I own both. I always found that "Cyclic and Collective" is a bit of a superset of the other, much shorter book. Having said this, "the art of flying" for years to me was the primary source of credible no-nonsense information on helicopter flying.
In the words of the author: "The first book concentrates on the basic[s]" using piston helicopters as examples.
"The second book goes into significantly more detail ... and is based around turbine helicopters with hydraulic[s]."
There is a significant overlap between the two books.