Could you explain a little more what you mean by a "quiet book"? When my children were very small, we had picture books we sewed out of cotton that they could have in their cots at nap time for example, but they were quite small.
My husband likes to read to fall asleep, and I admit the sound of his hands on the pages when he turns them seems surprisingly loud in the silence of our winter nights - not so noticeable during tree frog season!
So these are two interpretations of what a "quiet book" could mean, but maybe you mean something like "quieting the mind", so please expand on what you're thinking of?
Personally, I would use natural fibres like wool and cotton and silk. A lot of sensory books are actually made of polyester and other petroleum based fibres. I'd rather avoid plastics in my toddler/baby books. Little ones tend to learn about their books by chewing on them, and I'd rather the book be nontoxic.
The neat thing about using wool, is you can also felt it. Needle felting allows you to basically paint pictures in wool without any stictches.
Using a mix of cotton, linen, wool and silk gives lots of differnt textures for the kids. A sheep could be made of wool and water could be done with silk. If you had a page be a picture of inside a house, you could make the floor smooth silk, the walls made of cotton, the table with leather, the curtains with linen, and a cat made of wool. This would give a great, non toxic textural experience for the kids.
You could use a lot of tecniques for details, too. One could aplique certain things onto pages, and embroider other things, and still others could be needle felted on.
I would probably make the base for each page be of 100% wool felt, since it's nice and thick and sturdy. It would be easy for little hands to turn. Then the different objects and pictures could be needled felted, embroidered, sewn, or appliqued on.
I'm really wishing I'd had more time to make things like this when my children were younger. We had a few cloth books given to us, but they were all polyester. And, we couldn't afford to buy a natural one. I think if you're spending the time to make one, use natural materials. You could even find a lot of them at thrift stores by repurposeing old cotton/wool/etc clothes!