Oh that is a nice preface.
I'm buying this book mostly for the "collectibility" of the FLGS-exclusive version. I'm interested in the lairs and lore sections, and of course new/updated monsters, but I REALLY hope the whole thing isn't written like the preface. It feels to me like they heard us asking for more detail, like there was in the 2nd Edition monster write-ups, and decided to make us regret the request.
I'm more excited for this book now. I don't need another encyclopedia of monsters. The origins, dispositions, and lairs (LAIRS!) information interests me greatly, though, and since I like a cosmopolitan setting, the races would seem like a good fit. I'd get that book even if it just re-hashed the MM, so the bonus monsters are icing on the cake!
The conceit of this being Volothamp's guide is good "plausible deniability" territory, and lets WotC go wild with monster info while inoculating themselves against (most) cries of puriists. The Volo/Elminster interaction seems a bit twee, perhaps, but we shall see how that plays out!
Races of the multiverse? I wish we had a bit more info.
Actually in Game lore is very useful. Maybe Volo will present that while elminster gives correct answers. So depending on the PC you may give one or the other information.
Not going to lie, out of all the "Canon" FR characters, Volo is my favorite.