speaking of which
There is a shrinking book too. I remember this one very well.
"Help! You're Shrinking" was the title
http://www.fantasticfiction.co.uk/se...own-adventure/
Don't think that is it. I find some info on the forgotten planet.
http://www.amazon.com/FORGOTTEN-PLAN...926097-4165534
Might it been "War with Evil Power Master" ?