It seems that many of us are homeschooled as I am too! (In fact, my entire FTC team is!)
That would be pretty cool to write a book for RobotC, although I learned a lot from the RobotC tutorial videos, and that Whitman College "book" that magicode referenced. (great help BTW) Back when I used NXT-G, I bought some books that helped me with NXT-G and I'd imagine The book you plan on writing would be similar. It went from the basics of what the programming environment looks like, to more advanced stuff like data wires, multitasking, etc. I think a RobotC book would be very beneficial for a new programmer. Being the main programmer for my FTC team and with no one else with the know-how to do so, it would help many FTC teams as well. Mind if I jump in with ideas and editing? It'd be fun getting this out and published.
If you're planning on doing basic robot programming you're going to need some instructions for a basic robot that the readers can build to test what they write. Also, give thoughts and ideas for future programs, not included in the book to get the reader thinking. Those are a couple things that I thought were good in the NXT-G books I wrote.
edit: You could probably get some sample robot build ideas from here: http://www.nxtprograms.com/
There a lot of fun and easy robots to build on that site, with programs in NXT-G that could be remade in RobotC.