AU/AE primary spellcasters are kinda weak at low levels compared to other characters; they have minimal proficiencies and BAB, and their main offensive or defensive spells and abilities are rather pathetic until at least the lower-middle levels. You'll find a low-level magister, witch, greenbond, or runethane having a hell of a time even trying to hit an enemy in battle, because most of their offensive spells require a normal ranged attack roll, or in some cases a normal melee attack roll, and much less often, a melee or ranged touch attack. No Magic Missiles, Burning Hands, Rays of Frost, or the like, not even Shocking Grasps or Chill Touches to rely on. A low-level spellcaster would do well to invest in a feat to gain Fireburst (a complex 1st-level spell, the closest thing AU/AE has to Burning Hands) and then Earth Burst (a complex 2nd-level spell, resembles Fireball) if they want to have any chance of being useful in combat before finally gaining 3rd-level or higher spells. Otherwise, they'll need either high Strength or high Dexterity, because most other low-level attack spells require attack rolls, and most of them are normal rather than touch attack rolls.
I'd recommend having low-level casters invest in one or two proficiency feats, because a good martial or exotic weapon would help them defend themselves much better than any low-level spell would. A longbow or the like if they're fragile, a greatsword or the like if they have good Con and at least decent Str. Some mid-level and high-level spells also give some significant combat bonuses, so a spellcaster focusing on melee or ranged weaponry could be viable. Most of the time, I think, you'll be preparing utility spells like Acrobatics, Object Loresight, Safe Fall, and Charm, so relying on decent physical ability scores and weaponry may be a good thing. Mind Witches I find to be rather weak and lame, their witchery abilities aren't as useful or effective as those of other Witches (not to mention that several of the Mind Witch's abilities can be more or less duplicated by low-level spells), a real let-down for me. There isn't much in the way of good, low-level crowd control or mind-influencing spells, either. Low-level illusions are highly restrictive and more clearly defined than in the D&D Player's Handbook, and there's very little in the way of low-level charms and compulsions and such (the 1st-level spells Charm and Directed Charm just give bonuses to Charisma-based checks for social interaction, pretty much).
Be aware that AU/AE characters are not going to be healing as rapidly as in D&D; don't expect them to survive through multiple battles in a day. One or two weak battles, sure, but give 'em a single tough or mildly tough battle and they probably won't be able to survive much more in the same day. Not as much of a problem at higher levels, where magisters and greenbonds will finally have access to some good healing spells, and greenbonds will be able to heal a goodly amount of damage through their other class abilities. Champions of Life suck at healing though, regardless of level. Other classes have to spend feats to get any decent healing spells (though some sub-par healing spells are available as Simple spells).
The races don't really grab me, especially with so little info on them initially, and such simple stats; only Faen have any kind of interesting racial features, the rest are essentially a collection of skill bonuses with one or two ability score adjustments tacked on (and I don't even see the reason behind some of them; i.e. why the heck do Litorians gain a Dex bonus instead of Str, when they really look so much burlier and stronger than humans?). Verrik seem neat at first glance, but really their racial traits are pretty pathetic. Their minor psionic magic is of miniscule usefulness, their access to complex psionic spells when they would otherwise gain only simple psionic spells is a joke (there are hardly any spells with the psionic descriptor, and they're extremely limited in usefulness, plus most of them are already either simple or exotic), and their ability score adjustments aren't very useful in AU/AE (they're be better in D&D with monks, clerics, druids, and rangers; as it stands, they're mildly helpful adjustments for witches and some greenbonds, while making Verrik less capable as mage blades and champions).
I'm also rather disappointed with the extremely limited skill points and class skills of many AU/AE classes; at least in D&D, most classes with poor skill selection at least have a variety of spells and abilities that can compensate and keep the characters from being one-dimensional in their non-combat capacities. Mage Blades, while cool, are shackled by their Charisma casting stat (which is also important to their other class abilities), such that their skill points suck and their skill selection is horribly limited (think 3.0 Fighter + 3.0 Sorcerer skill lists). With their slower gain of spell slots, they can't compensate very well with spells when it comes to anything other than fighting, and they don't even fight as well as a Fighter (though they have at least a little versatility with their spells, and can manage a good but short-lived offense or defense). Far too many AU/AE classes are extremely limited in skills, and few of them have anything to compensate for this outside of combat.
Reading the anthology "Children of the Rune" was a good insight into the races and the Lands of the Diamond Throne, but didn't really detail many of the races or places very significantly (i.e. only a bit of insight into Litorian and Sibeccai cultures and mindsets, and Verrik only got a little insight into their mindset, but not their culture). The book focuses more on Humans, Giants, and Faen, though it has at least a bit on Mojh and the rest. It's a good book, but I shouldn't need it to understand the races and classes of AU/AE decently. Then again, I find it hard to believe some of the stuff the characters in the novel did, considering how incredibly limited the skills and abilities of their classes are in AU/AE (a mage blade prowling around almost completely unseen, without invisibility magic? yeah, right).
