Open Beta?

[Ouch!]

I think I'll buy the guide for this game to better understand the mechanics behind some things, though.

Don't waste your money. The guides don't know anything about the game's mechanics, and likely we won't for some time. The few releases of the FFXI player's guides insisted that AGI was the stat which affected ranged damage; in fact AGI affects ranged accuracy, while STR affects damage. That's the only one example of the vast misinformation that permeated those pages.

Published guides for MMORPGs are more likely than not utter tosh and not worth purchasing. Just keep up to date with the online communities for the game (ZAM, Eorzeapedia, etc.) for the most relevant and accurate information.