My question is: Does this mean the authors are saying that natural selection was not the cause of the evolution of the eukaryotic cell from the prokaryotic cell?
No. They're saying that complex life was dependent on the formation of mitochondria, and that this was apparently an event of unique importance. It's possible that similar adaptations from prokaryotes may have happened at other times, but that the existing eukaryotes thought they were tasty and/or out-competed them. Or that we just aren't aware of them - we aren't omniscient after all.
Nothing whatsoever in the material you quoted contradicts the theory of evolution. At all.
[qs]And if true what effect does that have for The Darwinian and neo-Darwinian theory of gradual descent by random mutution and natural selection? /qs
None. Random mutations of unique significance happen all throughout history. All vertebrates are related to a common ancestor, just as all eukaryotes are related to a single common ancestor. The development of the backbone was no less a singular and massively important development in the history of modern biodiversity than the development of mitochondria - without either adaptation, life on Earth would look MUCH different than it does today.
You could take basically any example of an extremely successful adaptation and say similar things.
But one-time mutations that make massive effects on the appearance of biodiversity a few million years later do not contradict the theory of evolution - rather, they support it.
The development of mitochondria allowed for the development of more complex organisms which were able to take over a rather large unoccupied niche and thrived. That's all, and that's exactly what we'd expect given mutation and natural selection.
Evolution doesn't require that similar adaptations, if successful, must happen repeatedly and independently. It does happen sometimes (see the eye), but evolution is not guided by anything more than survival and reproduction.