What word begins and ends with an E, but has only one letter?

Twice ten are six of us,

Six are but three of us,

Nine are but four of us;

What can we possibly be?

Would you know more of us?

Twelve are but six of us,

Five are but four, do you see?

What are we?

My thunder comes before the lightning; my lightning comes before clouds; my rain dries all the land it touches. What am I?

The dirtier I get, the whiter I look. Who am I?

What has to be broken before you can use it?

He digs out tiny caves and stores gold and silver in them. He also built bridges of silver and made crowns of gold. They are the smallest you could imagine. Sooner or later everybody needs his help, yet many people are afraid to let him help them. Who is he?

I have an eye but still cannot see.

Who am I?

I have no life, but I can die. What am I?

I am the beginning of the end, and the end of time and space. I am essential to creation, and I surround every place. What am I?

There are a number of books on a shelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?