Yes, the publication dates are correct. Talking to Dragons was published in 1985 by MagicQuest; the other three books are prequels.
These books owe a lot to the Oz books and the “Fractured Fairy Tales” segment of the old “Rocky and Bullwinkle” cartoons, and they were great fun to write. Dealing with Dragons began as a short story, “The Improper Princess,” and was expanded to novel length at the insistence of Jane Yolen, my editor at Harcourt. It, and the subsequent two books, tell the story of Cimorene, a fairy-tale princess who finds her expected duties boring and therefore runs away to become the “captive” princess of a dragon.
Talking to Dragons is told from the viewpoint of Daystar, Cimorene’s son, as he sets off on his own adventures and tries to piece together the past his mother hasn’t told him about.