Well, for something that was not meant to go on sale until tomorrow, its up now. I'm sorry, but this is a little bit of failure when something goes up for sale a day early. If supplies run out, those hobbyists that really want to the book, may be facing a long delay for ordering on the actual release day.
My suggestion is for those of you like me, get your order in right away.
http://www.games-workshop.com/gws/catalog/armySubUnitCats.jsp?catId=cat440161a&rootCatGameStyle=wh40k
Iyanden: A Codex Eldar Supplement $49.50
Iyanden: A Codex Eldar Supplement Special Edition $85.00
Lets hope that supplies are in full stock this time around. And yes, for a supplement, paying the full price of a standard codex is extremely high. It is 72 pages, 32 of which are background.