Amazon also has Barbara Hambly's novel
Dragonsbane on sale, which is an absolute steal for one of my favorite books. She tells an absolutely wonderful story within the basic framework of a quest to kill a dragon, though the story is much more than that base premise. It also has, in my opinion, the absolute best portrayal of a dragon done in fantasy.
It's completely standalone. Although she wrote sequels she did so about 15 years later and she never again managed to capture what made Dragonsbane so special.
Almost all of her other books are on sale, too, but this is only one that's an absolute must buy if you like fantasy even the least little bit.