I've got it.
I ran it once a couple of years ago. Unfortunately, I bumbled my way through much of it.
It's an awesome game in concept. Very big into character development and world-building. The problem was in implementation. The author (Christian Moore) was apparently trying to get his money's worth out of some 400 level English courses in college (I'll include some terms as I explain things). Also, the rules are really set up to be a very loose framework for roleplaying (mythmaking).
Several of us on the mailing list had gotten Christian's go ahead to do a second edition that was more "accessible", but it was an abortive attempt (for my part, I changed jobs and moved across state as things were just getting going). Too bad, too. It's got some real potential.
The highlights:
Aria Worlds (the blue book). If you do homebrew, you should have this book. Even if you don't follow the process completely, it's got some awesome questions in it and some ways to quantify things that you may not even think about normally. This book will add a lot of depth to any setting.
There are several different technology scales to help define exactly how advanced a given society is. The Isolation and Interaction scales also help to figure out how goods and technology flows between societies (Narritive Environments).
There's a section on societal customs, like values, basic government structure, rules of inheritance, etc.
One of the most unique concepts (and difficult to work with) is the Hierarchy of Social Estates. The HSE is basically a way to figure out who stands socially higher than whom. Who is more respected and has more pull -- the baker, the soldier, or the dock worker?
Aria Roleplay (the red book): A lot more to this book, since it basically covers everything else, including the following.
Character (persona) creation/advancement. Character points are based on age. Creation follows your path of development, almost from birth. At any given phase in your life, you'll be involved in a "Vocational Setting" (basically, a job or lack thereof). Based on that setting, you pick skills (expertises) that you develop. Basically, it's a mechanic that ensures that if you say you grew up in the desert, you don't sail like you were born on deck, but it can be rather in depth (and potentially frustrating).
There is a mechanic for character personality traits. It works a bit like the Storyteller system's Nature and Demeanor, but the traits have ratings from 1 to 10. You are expected to play "in character" based on these, but the values would also impact the difficulty of a Charm or Dominate type of spell.
Speaking of magic, the Reality chapter is not so much a magic system as it is a metasystem for creating the magic system you want. It's very loosely based on Ars Magica as a framework, but you could develop anything from D&D Vancian spells to Mage: the Ascension concentual reality. Some option would take a bit more work, of course, but they are all possible within the framework. The GM (MythGuide) is going to have to do some _significant_ upfront work, though.
If you want, you can go so far as to describe how hard it is to affect various materials with magic. You could also set it up so that certain objects served as vessels of magic energy (Omnessence) or even that a caster would have to return to a certain place to refresh themselves. Or you could have the "flow" freely available.
As an example, _my_ Reality used several types of magic.
--Thaumaturgy was based on the principles of words of power. All thaumaturgic magic fit into three categories for duration: Instant, Permanent, and "Concentration" (as long as the caster continued to speak the weaves, actually). Thaumaturgy excels at manipulating and conjuring energies, but it has difficulty actually creating anything and you can forget about directly impacting anything living. Thaumaturges are incapable of cooperative effects. Reckless use of thaumaturgy often results in burn-out.
--Rune Lore uses mystic symbols to tap into the energy inherent in various objects. Because of this, a rune actually consumes the object it is scribed upon -- rune casters tend to like stone. Rune casters are excellent diviners and passible healers, but have difficulty with energy. Madness often finds its way to rune casters.
--Witchcraft taps the energy of living things. Witches usually deliver their spells through potions, poltices, and the like. Most often, these mixtures contain herbs, leaves, and other plant components, but animals are even more charged with life than plants and fresh animal ingredients are often used for more potent rotes. Of course, humans are the highest of the animals and have the most energy within them. In extreme circumstances, witches have used (usually) willing sacrifices to power their greatest rituals. Also, witchcraft lends itself to cooperation and a large coven using a willing human sacrifice is capable of affecting an area of hundreds of miles, blessing (or cursing) the land for years to come. Witches are most known for their power to heal and harm those with whom they deal and are more than passible fortunetellers.
--Necromancy is the quickest path of power for those willing to take it. By burning souls, the necromancer harvests large amounts of energy which he can use to "force" his way through powerful arts. Most people greatly despise necromancers, though, because a damaged soul _never_ heals. Elves are especially wary of necromancers because they do not find final rest when they die, but are reborn -- with any necromantic scars still there. Someone who has had a bit of their soul drained away becomes less passionate (an impact to the personality ratings I discusses above). This is something they will never recover from.
Another interesting aspect of the Aria system is the inclusion of "Narritive History". Here, each player takes the role of a society and plays for a few years. There are rules for advancing (and losing) technology, military campaigns (not minatures, this is fairly abstract), coups, etc. Characters also gain XP during Narritive Time.
All this encourages the passage of time, so that (in theory) you have an organic game. Characters move on and their children may take up their roles. Events unfold over several generations of PCs, etc. Very cool idea. Helps to integrate the characters into the campaign world.
Even though we've gone the route of the very straight-forward 3E, I still refer to my Aria books on occasion. I think either of the books is worth getting, if you get the opportunity.
Here's a couple of sites to look at:
Geoza
Juha Vesanto's page
It's been a while since I've looked at either page, but Geoza was more complete last I looked. Still, Juha Vesanto is probably the expert on Aria (besides Christian himself), so I'd definitely check out his site.
Edit: oh, yeah. If you have any more specific questions, I'd be happy to answer anything I can. If you find the books and decide to run a game, _definitely_ post here first. I've got a whole list of stuff that I screwed up the first time and I'd rather save someone else the pain.
I'd never even heard of it. Tell, please?
