Welcome to ThereminWorld Joe_Sixpack!
The basic Clara Rockmore Method,
brief but very useful, is available freely;
among other places here's a link to the PDF on the Spellbound Page
http://spellbound.purplenote.com/RockmoreMethod.pdf
Carolina Eyck's method book is very thorough, effective, and nicely printed (though lacking an accompaniment CD which would have been very helpful).
http://www.thereminworld.com/news.asp?s=469 in both English and German.
a bit tricky to order from Germany due to limited payment options but well worth it.
The Robert B. Sexton Method Book "Method for the Theremin Vol. 1 (Thin air series) (Spiral Binding)" may still be available, it used to be at Moog Music but I couldn't find it this morning.
He uses the "wing" technique, and even that's not your style, it's a great collection of exercises and some really "on the mark" advice. [update: only found a used copy on Amazon]
It's a bit like an ear training book and those are useful for training exercises as well.
If you're willing to glean what you can from method books in other languages
Masami Tackeuchi's book is a fantastic primer and has a CD with it and just the music exercises and full pieces are a complete primer even if you can't read the text.
It's a bit expensive though from Amazon Japan (http://www.amazon.co.jp/exec/obidos/tg/detail/-/books/4907737416/250-2051605-9774613)
There's also used to be a free Spanish Method by Victor Estrada on line,
but I need to find a new link to it the one we have here seems to be broken.
Victor's site is http://www.victorestrada.com/
And of course try out the TW Search
http://www.thereminworld.com/websearch.asp
and also read through some of the technique forum threads here,
http://www.thereminworld.com/forum.asp?cmd=t&F=780
not an organized method book but there is **tons** of info on this all around ThereminWorld.
Hope that helps and of course keep us posted as you start you theremin adventures.