It's hard to give any reasonable answer, because it's all very dependant on your implementation.
But you could for example make a convention that all the inventory items will provide a custom property called "Description", so in each of the item scripts you'd add something like:
this.Description = "This is some log description of this inventory item";
And later when displaying the item close up, you'd have to keep track of the currently selected item, check its Description property and display it in the window.