I think the Raven Queen's backstory is presented in the Pluton entry in the Manual of the Planes.
I like the tomes, but one thing I definitely hope to see is the "Power swap" effect for Utilities, because some utilities really are case by case basis (Wall of Fog vs. Say, Invisibility), so being able to whip that sucker out when you need it would be nice.
I'm also pondering expanding this, and coming up with some Tomes for Clerics/Avenger/Invokers. I am starting to dig the idea of, say, using the Avenger to replicate the Archivist class from Heroes of Horror (Holding up a holy text and reading an esoteric holy chant to harm a devil, for instance). An Avenger multi-classed/hybrid-ed into Invoker might get that feel, perhaps.
Maybe my game preferences are somewhat different from most D&D gamers but as a player or master one thing that would cut all the fun and belief in campaign is a god talking to players asking for a favor or starting a quest.
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When I'm playing and a god show up all I think is "lame"...

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.