Book of shadows is personal and can be anything. It can be digital, or a written notebook. I take notes on my Android tablet, then write it down in a journal I found at Wal-Mart. When I first started by first BoS, I wrote it all down in Word and printed it out, slipped the papers into plastic sleeves and put them in a binder. So literally, it's however you want to make it. I hope this helps. :)
a book of shadows traditionally was made to write down the spells, rituals, experiences and other things magically related and then passed down through the generations...although modern day witches tend to make their own and sometimes multiple books of shadows...leather cover will protect your book from negativity and parchment paper makes it look cool...and if you want my advise i would go without lined paper...it makes it easier to make the pages look the way you want...good luck!
There's an excellent article with suggestions as to what you might want to put in your BOS at http://paganwiccan.about.com/od/wiccaandpaganismbasics/ht/BOS.htm
My BOS's are kept in a series of 3-ring binders...yep, in 30 years I've gone way beyond the ability of one binder to hold them all. Using a binder makes it easier to replace a page or rearrange pages as you wish. And you can even now find some 3-ring binders that have lovely cover art and even page separators with witchy images on them. Some truly elegant (and expensive) examples of the latter can be found at http://www.brahmsbookworks.com/grimoiremenu.html My real-life coven used one of these gorgeous books as our coven BOS. There are some smaller books that can be found here at the store on SOM at http://www.spellsofmagic.com/shop.html?c=B
These days I find it easier to keep my BOS on a stick drive for my computer. But I always back up my stick drive on a hard disc just to make sure that a failure of the stick drive doesn't lose my information.
As others have said, your BOS is a very personal magical tool. What you use to keep it in and what you chose to include in it are very much up to you.
i have a book of shadows for experiences separate from my spell book. both are on my laptop because im looking for a book that calls out to me as it were.
