Given the top two entries on this list, we have a great deal to be thankful for:
1. Valley of the Dolls Jacqueline Susann
2. The Adventurers Harold Robbins
3. The Secret of Santa Vittoria Robert Crichton
4. Capable of Honor Allen Drury
5. The Double Image Helen MacInnes
6. The Fixer Bernard Malamud
7. Tell No Man Adela Rogers St. Johns
8. Tai-Pan James Clavell
9. The Embezzler Louis Auchincloss
10. All in the Family Edwin O'Connor
I note this list because of the eclectic mix of things. I don't know that I ever realized that Helen MacInnes had at one time been a best-selling author. And Bernard Malamud! Who'd have thought such a book would make it onto a list of things read by many. Tai-Pan is among my favorite of the works of James Clavell. I like it a good deal more than Shogun, in part because it is a good deal shorter and packs a greater punch.
What is remarkable is that while Susann's and Robbins's names live on, most of the rest of these authors are more-or-less forgotten. Nevertheless, it is my guess that were one to google each of them, one would be likely to find a large number of entries dedicated to each. This is one thing that the internet has done for us (or perhaps to us). Fewer authors sink into obscurity (well deserved or otherwise).
Allan Drury is still very good. You can't do better if you are interested in politics. He has some tics, but they're not really annoying ones. The prominent one is that he refuses to use the words "Republican" or "Democrat". It's just the minority party and the majority party, and you can put your own construction on them. I thought this was pretty wise for a political author; keeps it current.
Capable of Honor is a very fun book, if it's the one I'm thinking of.
I like Helen MacInnes, just recomended her books to a friend. Malamud I don't care for, but I wouldn't say he's sunk into obscurity. Unless you mean the obscurity of being assigned in modern American literature classes.