Yes, of course I've read the books, and more than just the first, I've read all of the 14 Baum originals and some others of the Famous Forty; the only one I've read that felt really "Ozzy" to me was the last, "Merry-Go-Round in Oz". (When I was young, it was one of the few guaranteed ways of finding a good present for me: locate a new Oz book I hadn't read yet).
Polychrome was the first girl I ever fell in love with. Before I knew what that word really meant.
I have watched/read several non-canon works. Some I actually enjoyed, despite not thinking I would ("Tin Man" being perhaps the most surprising), while others I absolutely cannot stand (Wicked, A Barnstormer in Oz)
And obviously by FAR my major impression of Oz came from the books.
It's interesting that a fair number of those who have read at least some of the other Oz novels do not remember Polychrome; she plays a strong part in three Oz novels.
Of those who DO remember her, it seems fairly split between "Yeah, rainbow's daughter/rainbow fairy" and "I LOVED her!!!".
I actually find quite interesting that a significant number of people really haven't read the books, yet HAVE read or watched secondary materials. I'd be very unlikely to even TRY such things unless I was really into Oz, so the apparent popularity of such things is an interesting side point.
I'm still not sure what that says about whether Polychrome will be salable or not...