Okay, first things first. In order to sew a quiet book you have to know how to sew. Of all the skills you will ever learn, sewing is probably one of the most simple. There are tons of videos and instructions online to teach you how to sew so I won't rehash them here, but here's a link to a thorough and basic tutorial for pretty much everything you'll need for a quiet book: How to Sew Felt quiet books can be sewn either by hand or machine. I prefer machine sewing wherever possible because it is much faster for me, but I have friends who prefer to sew by hand so it completely a personal preference. Another option for putting together a quiet book is a hot glue gun. This is a very simple, inexpensive, and quick way to make a book.
Supplies for a quiet book are also fairly basic – unless you get carried away and want to embellish your pages. Then you can get as wild as you like. 9X12 craft felt sheets are the most common material and can usually be found for about a quarter each. Amazon sells a very nice large package of felt in multiple colors that will last for several books. Your local crafting or hobby store probably also carries craft felt both in sheets and sold by the yard. There is a wide variety in the type of craft felt available such as glitter, stiffened, adhesive, and embossed.
The main thing to keep in mind about craft felt is that it is not actually wool. Usually made out of acrylic, polyester, rayon, and/or viscose, it is the cheapest material available for felt quiet books. If you really want to be environmentally friendly with your quiet book, there is also felt made out of recycled plastic bottles called Eco-fi or a bamboo/rayon blended felt branded Xotic. While stiffer than craft felt, either of these choices will work for quiet books. Both are also more costly than craft felt. Blended wool felt is another possible felt. It will last the longest due to its sturdier construction. However, do keep in mind, it can be more difficult to sew with due to the texture.
Other supplies you will need include needles, thread (matching your felt is optional), a good pair or two of scissors, and any embellishments you desire. A few common embellishments include buttons, clear vinyl, snaps, velcro, ribbons, sequins, buckles, etc. Don't feel like you need to buy a lot of embellishments. Some of the most unique and interesting pages are made with recycled embellishments. For example, an old pair of buckles from overalls or clear vinyl from a blanket storage bag. If you want a page to crinkle, a baby wipes bag or chip bag is the best material I have found to make a loud crinkle and is a nice and cheap option.