An Arabian Nights coming-of-age novel, Darren Shan's The Thin Executioner details the adventures of Jebel Rum on his journey to recover his honor and win the woman of his dream, Debbat, the high lord's daughter. Born into the quasi-aristocracy, Jebel has a slim build that makes becoming an executioner like his father or a warrior doubtful. He won't accept lesser positions as a teacher, judge, or trader. Then, when his father announces his retirement so one of his older sons can enter the mukharyet and claim the title, he omits Jebel and thus shames him. Jebel decides he must undertake a quest to become invincible so he can win the competition for his father's position to reclaim his honor and marry Debbat.

Questers travel by foot on an arduous journey through hostile territory, and when they arrive at the mountain of the god, they must kill the slaves who accompany them. Debbat dislikes Jebel and derides his abilities. She reminds him the quest entails a long, difficult journey, many dangers, and the killing of a slave. He has none and no funds to buy one. Certain, Jebel will fail, she agrees to seek her father's permission, hoping to rid herself of him and gain reflected glory because he undertakes the quest in her name.

Jebel has no money to buy weapons, supplies, or the essential slave. His father won't allow slaves in their household. To remedy this, he goes to Fruth, the city where slaves live, but has no idea how to find or acquire one without money. Luckily, he meets an old friend of his father who knows just the man, Tel Helsani. The slave has a family and agrees to the quest for their freedom.

All questers must have the approval of the high lord. With Debbat's help, her father blesses the effort and gives Jebel the money he needs. Jebel's contempt for his slave increases the difficulties of the journey, but the man remains steadfast in his efforts to free his family and protects Jebel from others.

The journey proves arduous, but goes well at first. Soon however, dangers occur. Thanks to Tel Hasani's wisdom, they progress, but Jebel's patience and beliefs are tested every day. They must travel though hostile countries, deserts, and marshes. The quest challenges Jebel's beliefs and values. Many turns of fortune await them and confuse Jebel.

While Shan follows the traditional quest pattern, he uses the Arabian Nights setting to develop a number of themes including slavery, war, honor, self-sacrifice, and death. His characters overcome adversity and meet interesting people with belief systems differing from Jebel's. Fantasy elements with the various gods enliven the narrative. The ending proves satisfying, but in unexpected ways for Jebel.