Three thoughts:
1) I expected the title to be "Elemental Evil Adventurer's Handbook" not just "Adventurer's Handbook". The latter sounds far too generic and not storyline specific with the title being so large and the little corner logo being so small. It will be harder to have an Adventurer's Handbook for other Adventure Paths without possible confusion.
I imagine this accessory *could* be a little more generic to serve as your standard splatbook in addition to player sourcebook on elemental evils. But that's a little lame when elemental power is such a cool theme in and of itself. There's nothing in the cover or title that screams "this is the book if you want to make an elemental themed character!!"
2) The covers are kinda bland. I'm not getting "phenomenal elemental power" from the Adventurer's Handbook. I'm getting pissed off druid. Ditto Princes of the Apocalypse. It doesn't seem very culty or Evil Elemental Eye-ish. Is that meant to be an evil sylph?
3) It's neat to see the covers. But what I *really* want to know is the pagecount, to see if they're large enough to justify the expense. Or if they're little tiny things. We know they're $40 and $50 respectively. As it's priced the same as the Core books, is the adventure a 320-page book? Or is it 200-pages, like two Tyranny of Dragons books combined? Is the Handbook at *least* 200-pages as well? (If so, why is it $10 cheaper.)