There are several reasons for this. Let's start with the most basic: its appearance. Has D&D ever had a cover for a product as provocative as this one? I know I'm widely regarded in these parts as a stolid stick-in-the-mud, so I hope I won't shock anyone by saying that I really like this cover and not just for obvious reason. What I like here is the simplicity, the starkness of the piece. It's a very suggestive illustration, one that gets me to thinking of Robert E. Howard and Clark Ashton Smith and other writers from the Golden Age of the Pulps. There's also a subtlety to it that I appreciate. Yes, it's an illustration of a naked woman, her hands bound, and laying on a (possibly sacrificial) slab, but, aside from the nearby brazier, there's no real context or action to it. We have to fill in the rest for ourselves. Let me also say that, on some level, I also think the illustration speaks volumes about how the cultures of both the hobby and the industry have changed since 1976, when Supplement III was first published.
The interior of the book is still recognizably that of an OD&D book, but you can see the signs of the format I'll come to associate with AD&D. That's a good thing in my opinion, because, for all my love of OD&D, I'd never argue that its presentation couldn't have stood for some improvement. Eldritch Wizardry is also sees the re-appearance of David Sutherland, whose art strongly resonates with me, despite its flaws. Gone is Greg Bell, whose art filled the little brown books and Greyhawk. We also see the greater use of different type faces -- a small thing perhaps but another shift that shows TSR is becoming more "professional." They're still not quite there and Eldritch Wizardry is still clearly a product of hobbyists for hobbyists, though a much more polished one than previous supplements. For me, that's the sweet spot, so to speak: gaming products by "amateur professionals."
The content of Supplement III, like all OD&D supplements, is a mixed bag. There's a vague thematic element to the book -- "ancient and powerful magic," says its subtitle -- but to attribute anything like an organizing principle to an OD&D product is foolhardy. Still, if you squint your eyes and are charitable, you can see some connections between the various bits included in Eldritch Wizardry. And it's these bits that really get my juices flowing.
- Druids: I have a love/hate relationship with this character class. I think an alternative to the quasi-Christian cleric is a good thing. I also like the somewhat "morally ambiguous" presentation of the druids, which were first presented as a "monster" in Greyhawk. It's noted that druids have a mean streak to them, meting out punishment on those who violate their ethos. Of course, the druid has been thoroughly de-fanged over the years, becoming an airy-fairy tree hugger and I can't stand that. Likewise, the druid is a heavily based around the wilderness, which makes it a much more "situational" class than many others. Still, I can't deny that I have a soft spot for the druid.
- Psionics: Another thing for which I have a love/hate relationship. Gygax famously stated that the inclusion of psionics in D&D was a mistake. I'm not so sure myself. I agree that not every setting needs psionics. Furthermore, having psionics and traditional magic exist side by side can sometimes be too much. Nevertheless, I think there's a place for mental powers in D&D, if only to offer an alternative approach to "magic" that has a different metaphysical and mechanical basis. Indeed, if one's goal were to construct a setting in line with many pulp fantasies, something like psionics might work a great deal better than D&D's standard magic. I will grant that psionics, as presented, is a bit more complex than it needs to be, but, even so, I feel a frisson every time I re-read the psionics rules. Call me sick if you wish.
- Demons: Eldritch Wizardry finally gives OD&D some demons and they're simply terrific. Much as I have always preferred devils for their grandly medieval hierarchies, demons really scratch my pulp fantasy itch. These guys are freaky aberrations for the most part, the stuff of nightmares rather than folklore (for the most part). Some of them are so freaky they even have 10-, 12-, and 20-sided Hit Dice. We're also treated to the Gygaxian penchant for systematization: demons are divided into "types," with the balrog finally finding a new identity under which to set up shop without fear of legal reprisal.
- Mind Flayers and Intellect Devourers: 'Nuff said.
- Artifacts and Relics: Truly the jewel in the crown of Supplement III, artifacts and relics are something I have long wished D&D had expanded upon and developed further. I simply love the idea of magic items whose powers and abilities vary from campaign to campaign. I also adore items that have histories and contexts beyond their purpose in play. And who doesn't get a thrill when they hear the names Vecna, Lum the Mad, Baba Yaga, and St. Cuthbert? I've long argued that magic items need to be more magical. Well, you can't get more magical than these artifacts and relics, which often possess powers and functions that are both quirky and potentially dangerous, just as magic items ought to be.