I really liked this little book. It's a quick read, but inspiring. Another reviewer here recommended traditional runes, but I, for one, have always been left a little flat by traditional runes, which are Norse in nature. I'm just not drawn to Norse mythology or systems, but this system is based on Pictish symbols (she claims), much more comfortable for me personally. I'm also quite drawn to 13 stones as a good number for a Witch. I'll just add that I do use tarot as well, but I like to have a variety of tools to choose from.
I liked this book, and while I plan to slightly change some of the symbols on the stones to fit me personally, the system is a basically sound one, the writing is pretty solid, and making your own runes--whatever system you use--is a good way to make a solid connection with your divinatory tools.