I recommend The Man Who Counted, an amazing fiction book about a fictitious mathematician called Beremiz Samir and a traveler called Malba Tahan.
The first two chapters tell how Malba Tahan was traveling from Samarra to Baghdad when he met Beremiz Samir, a young lad with amazing mathematical abilities. The traveler then invited Beremiz to come with him to Baghdad, where a man with his abilities will certainly find profitable employment. The rest of the book tells various incidents that befell the two men along the road and in Baghdad. In all those events, Beremiz Samir uses his abilities with calculation like a magic wand to amaze and entertain people, settle disputes, and find wise and just solutions to seemingly unsolvable problems. In the first incident along their trip (chapter III), Beremiz settles a heated inheritance dispute between three brothers. Their father had left them 35 camels, of which 1/2 (17.5 camels) should go to his eldest son, 1/3 (11.666... camels) to the middle one, and 1/9 (3.888... camels) to the youngest. To solve brother's dilemma, Beremiz convinces Malba to donate his only camel to the dead man's estate. Then, with 36 camels, Beremiz gives 18, 12, and 4 animals to the three heirs, making all of them profit with the new share. Of the remaining two camels, one is returned to Malba, and the other is claimed by Beremiz as his reward.
ADDED:
- The Man Who Counted at Amazon
- A nice review at Math Hombre