Treasure Hunters: The Ultimate Quest is book 8 in the Treasure Hunters sequence. Nine adventure novels follow the Kidd siblings around the world. The publisher numbers the books in one continuous sequence. It follows Treasure Hunters: The Plunder Down Under and should be read after that volume. Readers new to the series should begin with Treasure Hunters and follow the numbered publication order, which preserves the characters’ continuing development and the story’s intended progression.