It's a short book... briefly, it's about a farmer (Giles) who by dumb luck and a blunderbuss (stuffed with nails, bits of broken pottery, bones) protected his village from a wayward giant and prevented further damage.
Giles becomes the toast of the town for his deed. All was well for Giles:
Giles (along with his dog named Garm), was equipped with a sword that was hastily given to him by the King (since broad swords were not in fashion at the court at that moment).... a sword that has mystical abilities to 'sniff out' dragons that are within a 5 mile radius. He was given the sword prior to the dragon coming, in payment for what he had done to the giant.until the dragon came
Members of the town successfully convince Giles to hunt the dragon named Chrysophylax (and alittle Dutch courage from ale he had been drinking).
He gets the better of the dragon - thanks primarily to the sword (Tailbiter) that appears sovereign in such matters involving dragons. The dragon's wing impaired he starts running away to be chased by Giles on his mare with Tailbiter waiving about in the air.
Exhausted from the chase the dragon collapses in front of a church and begins to bargain with the Giles and the townfolk for his life:
"Good people, and gallant warrior," he panted, as Farmer Giles rode up, while the villagers gathered round (at a reasonable distance) with hayforks, poles, and pokers in their hands. "Good people, don‘t kill me! I am very rich. I will pay for all the damage I have done. I will pay for the funerals of all the people I have killed, especially the parson of Oakley; he shall have a noble cenotaph—though he was rather lean. I will give you each a really good present, if you will only let me go home and fetch it.
“How much?" said the farmer.
"Well," said the dragon, calculating quickly. He noticed that the crowd was rather large. "Thirteen and eightpence each?"
"Nonsense!" said Giles.
"Rubbish!" said the people.
"Rot!" said the dog.
"Two golden guineas each, and children half price?" said the dragon.
"What about dogs?" said Garm.
"Go on!" said the farmer. "We‘re listening."
"Ten pounds and a purse of silver for every soul, and gold collars for the dogs?" said Chrysophylax anxiously.
"Kill him!"