Good fluff is also not a universal experience. Over the past few years, I've realised how irrelevant Monte Cook's work has become to my campaign.
Arcana Unearthed, for all the people who like it, has no bearing on my classic D&D game, and the mini-planar settings of
BoEM III - The Nexus are similarly useless. (That's not useless to everybody, but they're not likely to be used in my game).
Meanwhile, I showed my players the
Planar Handbook on Sunday, and they were enthralled. They loved the rules mechanics, and they loved the descriptions (fluff) of areas like the planar touchstones and the organisations/prestige classes.
So, would I like
Beyond Countless Doorways? I don't know... but given how underwhelmed I've been by Monte Cook's material of late...
Is there a moral to be drawn from this? Yes: There are many paths a gaming supplement may use, and each one attracts a different type of gamer. There is some overlap, but there is not One True Path.
Personally, I feel that the "fluff" content of the Wizards books has been increasing - but because it is always tied to solid game mechanics, people look down on it. (If you want a completely fluffy book, get a Wizards novel - they do a lot of those!

)
Cheers!