I don’t have a Book of Shadows.
I tried to have one once upon a time. It was in a three ring binder (so I could insert, remove, or rearrange pages) and it had a few rituals and a bunch of pretentious essays on what I believed, what I had learned, and what I did. I still have the thing, but I regard it as an artifact of my past practice, and not a BoS that I refer to in my magical or devotional work.
I have a OneNote folder with old rituals I’ve done, and I suppose I can count that as kind of a BoS, although I think of it as more of a reference of things I’ve done than as something I go back to for a regular practice. But I’m more of a journaling type of mage. I record the time and conditions of ritual work and the goals of magical work, and the results of anything I do. I have lots of journals (mostly incomplete ones at that).
So what’s the difference?
A journal is for personal reference. I’m the only one who will see it, excepting rare occasions on which I may ask a trusted associate to review something. For the most part, it is written by me and addressed to me. So I leave a lot unsaid, because I don’t need to say a lot of it. I don’t need to explain a lot of stuff to myself, or justify why I did or thought certain things. I record physical and emotional conditions I might not remember, but I don’t usually forget my philosophical positions. And when I do journal on such things, it is to remind myself, not explain or justify.
A Book of Shadows, however, is written for other people. It is to pass on rituals and traditions to other people who may not have been there when they were devised or implemented, or who may not understand fully why things are done the way they are. It is a way of bringing people into the fold, of sharing with them what they have missed, and of preparing them to join in to work others are already familiar with. It is stylistically different from a journal, and if you’re a solitary practicioner, it’s extraneous.
So I keep my journals. Someday, I may have a group that develops its own traditions, and we may build a Book of Shadows. And that BoS may include items from one of my journals. But as long as I’m by myself, I don’t really need to pass any traditions on.