Good luck with the writing and the taking-up-knitting! It's wonderful that you're planning on knitting chemo caps, and I hope the e-book covers that. I think knitting in the round is much easier than most people think, and I feel like the traditional "teach them to knit a garter-stitch scarf, then teach them the purl stitch, THEN teach them to knit in the round" is not necessarily the best route.

I'm sure people have already shared this link with you, but if you find videos to be a helpful aid for knitting, this site comes highly recommended:
http://www.knittinghelp.com/

It has videos for the three major types of circular knitting under "Advanced Knitting Techniques".
http://www.knittinghelp.com/videos/advanced-techniques