"The Adventurer's Handbook" is not the right title for that book. It sounds like something that would apply to all characters, from all settings and campaigns. If they want to make an elemental evil-themed character creation book they should call it one!
As for their taking elemental evil to the Forgotten Realms, that is about as good as taking the most famous stuff from there to Greyhawk. I wish they would stick to the original settings, and systems. There are consumers interested in elemental evil and Greyhawk, and many of them still play 1st Edition. Why not release this for 1st Edition, and let everyone else who is interested convert it to their favorite edition instead of asking the original fans to convert it?