Where can you buy the book of shadows?

Yes, You can buy a replica of the actually book of shadows used in the charmed series with all spells/family history/info etc as seen in the series at www.lapuliabookofshadows.com/

be warned, it's expensive it's genuine leather and custom book binding.

Yes, you can also buy genuine book of shadows at the same website that are custom made with blank parchment so you can create you own .

You can also make your own book of shadows anytime it doesn't have to be some fancy custom made leather book, it's really just a notebook that you make special by what you include within it's pages.