Meh... I'm sorry, but McCaffrey was not a good writer; her prose was awkward.
There seems to be a bunch of writers specialised in the fantasy genre who keep on churning stuff by the truckload, and most of it is really bad... McCaffrey was one, Raymond Feist is another... I call it "literary diarrhea".
As a hard-core science-fiction reader born and raised in Europe, I always wondered about the somewhat dubious reputation of this genre in North America; after arriving here, it seems to me that a) science-fiction is often too often conflated with (children's) fantasy (even though they should really be separated!) and b) there's an inordinate amount of endless series (serials?) that occupy lots of shelf space in bookstores and libraries, drowning in noise the real masters.
I think that book series are a manifestation of literary dilution, and they seem to "calcify" writers in familiar patterns. Even some of the most deservedly famous among them have weak books ("Dune" come to mind, "The Foundation" is another example, and even the "Ender" series has petered out [sic!] beyond the third volume); don't get me started on series that take a life of their own and are maintained by writers who have very little in common with the original author.
Honestly, I think the temptation to write endless series come mostly from their steady financial promise and appeal. Very few writers do so because they really have good direction and development.
But, in reality, most of the *really* good books are standalones (or singletons).
