It is not my first book. Or even my second. To date this is my third book on witches.
My first was a "netbook" called "The Complete Netbook of Witches and Warlocks" for the 2nd Edition version of the game. It was totally a fan-driven work and most of it had been written for the 1st Edition version of the rules. Back then the file on my computer was called "thewitch.doc".
This original "thewitch.doc" was never really meant to be seen by anyone but my gaming group. Indeed, I figured I'd be the only one to ever play a witch character. I took a Magic-User character I had rolled up with the idea of playing her like a witch and then stopped her MU advancement and started her out as a 1st level witch. Occult Powers were spells back then and all I had was a list of spells from the Cleric and MU lists that I felt were "witchy". That document grew to become the "The Complete Witch" and then finally "The Complete Netbook of Witches and Warlocks".
The CNoWaW was in my mind a great sucsess. I released it between October 28th and October 31st of 1999. In fact I remember sitting in the hospital room right after my first son was born posting it on a laptop while my wife and new baby slept. Well that baby turned 13 over this past weekend! Kinda nice that my newest Witch book was released 13 years later.
After that in 2002 released "Liber Mysterium: The Netbook of Witches and Warlocks". This one was far more polished and I considered a "real" release. It used the OGL and the d20 logo. I worked with what was then called the FANCC, or the Fantasy Community Council. Their goal was to make and release quality netbooks that adhered to the OGL. Many of the members would later go on to do other things. I went on to Eden to work a number of their books including WitchCraft, Buffy and Ghosts of Albion.
In the case of all my books I would go back to my ever evolving research notes. Pictured above and below is just one of maybe 4 binders of information I have collected over the years. One of the print outs has a date scrawled in red pen (former teacher here!) of March of 1997. I know I have some materials even older than that. Lots and lots of notes.
In every case and especially when starting a new project I like to go back to my notes. Revisit old ideas, question why I rejected some and kept others.
The Witch is different from the CNoWnW or LM. While in each book the witches have "Occult Powers" their mechanisms are different. Each witch can for example cast "Wave of Mutilation", but how it works is slightly different. Complete Netbook witches are akin to that edition's Priests. Liber witches are more like Wizards. The witches in The Witch are something new. Older versions of my witch needed high Wisdom as their primary stat. Witches in The Witch need a high Charisma.
It is a ritual for me to go back even further when I start a new project to go not just to my notes, but my primary sources. For the Witch I really wanted that feel of a game supplement from the late 70s early 80s.
You can still find my older books online, I don't link them here really for a couple of reasons. First they were done a LONG time ago and I would like to think my writing has improved significantly since then. Also, at least in the case of CNoWaW, they are predominantly fan works and written under that assumption. Those assumptions are not the same that The Witch (well and Liber) was written under. While I don't explicitly state any compatibility I did do a lot of playtesting to make sure that The Witch works with what ever version of the Basic Era game you are using, be it the original games or the newest Retro-clones.
You can read more developments notes under the Basic and Witch tags (there are a lot though).