As the "cover" of the pdf notes, Wayfinder's Guide to Eberron is a "campaign prototype"; the material therein is still in playtest, not yet deemed official rules content, and definitely not sanctioned for Adventurer's League play. Nevertheless, the rules in the book have been crafted largely by Keith Baker: "Bear in mind: this book presents my vision of Eberron. This is the world I run at my own table, and the way that I’ve converted its ideas to the fifth edition rules. All of the material here is presented for playtesting and to spark your imagination." Even if Wayfinder's Guide isn't the final word on Eberron in fifth edition, it's cool that they gave the setting's creator the opportunity to kick around in his own sandbox.
CHAPTER ONE: WHAT IS EBERRON? First, we get a basic explanation of what Eberron is all about. I like that instead of launching into a gazetteer or geographic details, the explanation instead speaks to the setting's themes and aesthetics. Eberron is a setting where magic has taken the place of technological advancement, resulting in lightning rail trains, airships, etc. It's not steampunk per se, but the difference has always been small enough that it's doomed to be called steampunk anyway, much to Keith Baker's chagrin.
Taken as a whole, one of the strongest elements in the setting is its pulp roots: the ideas of larger than life action and mysterious artifacts in far-flung locales just waiting to be found hits the Indiana Jones vibe pretty hard. In contrast to that, the setting also has a pronounced film noir component that makes D&D's usual "this race is evil, this race can be trusted" shtick unreliable--and therefore more fun.
My favorite bit, and the one that often seemed to get the least attention in previous Eberron books, is that the setting's current era is an inter-war period--it feels like World War I has recently ended and the possibility of a World War II looms heavily on the horizon. Well, except the "Mourning" has always struck me as a magical-apocalyptic take on the bombing of Hiroshima and Nagasaki, and the horrific aftermath that would entail.
Each of these setting elements gets expanded upon in its own section; the writing is fairly tight by WotC standards, and there is a good use of random tables and bullet-point lists to convey important information quickly. You might even be able to get a player to read about the setting before they sit down to play. The art seems to be mostly cribbed from prior Eberron products, but I've always liked Wayne Reynolds's style for this setting.
Generally speaking, I also like the attitude expressed in this pdf. It's noted that everything in D&D can have a place in Eberron, but also that the baseline assumption is Your Eberron May Vary--it's nice to see it explicitly called out that even though the setting has quite a bit of detail, your version of it doesn't have to cohere to the creator's vision and that personalizing the setting is encouraged.
Next chapter: Little Red Khorvaire, baby you're much too fast.
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Shameful self-promotion: My setting book, Krevborna: A Gothic Blood Opera, is currently on sale as part of DriveThruRPG's Christmas in July event!