Here is your best place. Don't buy any of those books or strategy guides that you see advertised on places like Ebay or whatever. Best case scenario: you pay for a book with info that you can get for free here. Worse case scenario (and most likely scenario): the info is outdate and/or flat out wrong. Do some looking around on this site and ask questions here (without being an insistent little prick if noone answers you in 10 seconds as we've seen with some others before {yes, I'm talking to you LadyP}) and I'm sure people will go out of their way to either answer you or direct you to a place that has the info you need.
Some highlights (don't have time for details atm):
LDoN: Instanced dungeons for just your group. No repops so you don't have to worry about mobs popping behind you. Some decent rewards dropped in the adventures and bought with "points" that you earn for completing an adventure successfully.
GoD: Mostly high level zones. Some crazy equipment. Some fun scripted events (again, for higher levels). The progression is insane.
Omens: Again, mostly higher level stuff, but some mid level stuff too. Some crazy mid level twink gear available.
More to come later...