One of the aspects of D&D I've never really liked, and part of the reason I drifted away from the game for almost a decade, is the magic system. You can't really talk about "realism" in magical systems without sounding like a pretentious idiot, so about the best justification I can offer is that it didn't match the expectations I had developed from reading The Wheel of Time and Darkover and The Dark is Rising, and all the ways I found to fix it either increased the disparity between casters and martial characters--spell points being the most obvious example--or required a ton of work, like rewriting all the spell lists.

Well, I'm sure that Spheres of Power required a ton of work, but I didn't have to do it. And it provides a completely new magic system that turns D&D's magic from "lighting candles to literally doing anything" to one that requires casters to focus on a few specific areas.

Gone is the arcane/divine split. Gone are long lists of spells. Instead, there are twenty spheres, each of which has about twenty talents to modify them. A wizard with the Destruction sphere can throw blasts of concussive force at nearby enemies, and can take talents to allow them to throw lightning or fire, hit enemies further away, or create explosions. One with the Warp sphere can teleport nearby, and can take talents to teleport further, teleport enemies, or cross dimensional barriers. And so on with Alteration, Creation, Detection, Life, Mind, Nature, Telekinesis, and all the other spheres. Access is controlled by spell points, which most--but not all--talents require and almost no base sphere abilities do. And spell points are relatively limited. A 20th level Incanter, the most magic-focused class, won't have more than a couple dozen.

This is great. One of the major problems with D&D magic is that wizards can do their job and everyone else's job as well, and the solution to the problem has always been to force them to pick an area of competence, but previous attempts rarely went far enough. And the at-will sphere abilities means that low-level wizards don't have to cast their couple spells and then pull out the crossbow for the rest of the day. You can have pyromancers and diviners and necromancers and shadowbinders and demonologists and all the literary kinds of more focused wizards without requiring custom spell lists and without requiring a player to deliberately limit themselves for the sake of the concept.

I don't usually like effects-based magic systems as much as I do exception-based ones, because saying, "I cast Melf's Minute Meteors!" is much more interesting than saying, "I use Destruction and spend a spell point for the frost blast talent." However, Spheres of Power includes several subsystems to allow for the best of both worlds. The Ritual system is a way to import existing D&D spells into the new framework, so the game can still have spells that the existing spheres can't easily replicate like animal messenger. The Spellcraft system lets wizards combine sphere effects to create unique powers only they know, two examples of which are a Destruction/Mind combo that freezes the targets with ice and slows their thoughts as well; and a Nature/Protection combo that coats the targets in vines that provide armor and grapple their enemies. Finally, the Incantations system is ported over as well. There's an embarrassment of riches.

There are new classes, which seem to work well but are hampered by uninspiring names. The Incanter is the one with the most spheres, the Thaumaturge is one that focuses on demoniac powers, and the Armorist creates a personalized set of weapons and armor, basically like a magical girl. I guess it's because archmage, warlock, and soulknife were already taken. Fey Adept and Shifter aren't so bad, but are still a bit uninspired. That's the disadvantage of coming in a bit late, though.

There's a section on adapting the magic system to the world, with a system of boons and penalties available to create magical traditions that can only use certain parts of spheres--lycanthropic wizards who can only use Alteration on themselves, for example--require staves or gems to use magic, need gestures and words of power like traditional D&D wizards, suffer Constitution or hit point damage to use spells, can't use certain spheres at all, and so on. The example given is a world where all magic is performed by elemental martial artists who control their powers through katas, which probably sounds familiar to you.

There's a few example worlds and organizations implementing the rules, but each world is only a little over a page. There's essentially no fluff at all except for those worlds and a few chapter fiction pieces, but really the book is packed full already and there's no reason to make it longer.

Without exaggeration, Spheres of Power is exactly what I'm looking for in a magic system for D&D and is probably the first book I've read in over a decade that made me seriously consider running a D&D game. If LFQW is getting you down, or if enormous spell lists are becoming unmanageable, or if you're sick of having to account for Scry and Fry when planning anything above 10th level encounters, check it out.