Now that i have played a few solo games im starting to get tired of lugging gear back and forth to be sold in the early stages of he game. I have started to make a magical book that summons forth a Djinni who can teleport you to the Adventurers Mart etc. My question is who should have such an item in their loot, or should it be sold at a shop?

Hmmmm... sell it at the Adventurer's Mart.

"Need to sell loot fast and the nearest merchant is a mile away? Let Adventurer's Mart help you with this Djinni! A quick Dimension-Door and voila!"

A very good idea, and yes, the natural person to sell it would be Ribald. Just make sure that you can get it no earlier than Chapter 6 (of course, you already knew that), and that it vanishes after you beat Tree of Life Irenicus (you might write in how the magics of the Djinn were irrevocably altered by entering Hell, or something).