Why are islands where people always assume they might get stuck with ten books deserts?

This doesn't appeal to me at all.

If I remember correctly, although Gilligan's Island was referred to as a desert in the ditty, it did appear quite lush.

I might go live on Gilligan's Island, and then again, I might not.

I might bring some books given fair warning,

though I am not yet prepared to divulge the contents of my valise.