Gods of Forever!
Within the Cage, your better:
The Lady of Pain.
I mentioned that I won The Plane Above from Robot Viking, & well, it came & I read it & found myself happily surprised. So that being said, let me get the "Con" out of the way first-- there aren't any character options in this book. I didn't think there were going to be. That doesn't fit with the 4e publishing strategy. I get it, I guess; there were grumbles about "having to buy" a book just to get the feat you wanted. Personally I thought those were stupid complaints; you don't have to buy anything, & besides, Wizards of the Coast is in the business of trying to sell books. It isn't foul play to...try to get you to buy books? They are a publishing company. It isn't unscrupulous of them to produce quality content in order to "trick" you into buying the book. Anyhow, WotC has segregated content in the fourth edition; books like Players Handbook 2 & Arcane Power are chock full of powers & feats; content for players (& I tend to be fundamentally unsatisfied with them, but that is neither here nor there). Books like Underdark & The Plane Above have Dungeon Master content (& I tend to think they hold up better). So yeah, I'd probably like a few "Astral feats" or something in here, & I'm personally not going to get a lot of use out of the monsters & encounters present, but by focusing on setting & plot hooks, it provides content that will outlast the moment. Just like you might buy an old Planescape book or Fiendish Codex to mine for ideas, you can pick & choose from The Plane Above with no qualms, & that is a major selling point.
The best thing going for this book are the Dominions, if you ask me. I'm still sad about the absence of the Great Wheel Cosmology, but you know, they could always publish an "Alternate Planes" book & fix that; or heck, why bother-- if you want it, just buy some of the older edition's stuff & bang, there you go. The Dominions are interesting, though, & are super interesting if you just turn your head sideways & look at them as something more than just divine realms-- if you look at them as pantheons. The lack of pantheons in Dungeons & Dragons has been a major pet peeve of mine from the beginning, & part of that is the idea that nobody would pray to an evil god who wasn't evil. That just isn't so. Lets look at Vecna, the god of necromancy & secrets. Listen, I don't know how to tell you this, but people have secrets. Good guys have secrets! Heck, if you want to keep someone's surprise birthday party under wraps, whisper it to Vecna; the fact that he knows your secret should appease him enough to help you keep it. Even seemingly awful gods like Torog, god of jailers, you might want to appease-- you know, give him a sacrifice so he keeps your uncle safe when he gets sent to the prison aisle for speaking out against the wicked government or something. & besides the evil gods, it seems silly to think that the worship of multiple deities isn't commonplace. Dominions are a great way of clustering them together. Heck, if you ask me, the gods of good & evil should be a little more mixed, even; put Bane in with Erathis as the military hedge that keeps her cities safe, put Gruumsh under the mountain of Celestia, kept prisoner by Moradin & Bahamut & Kord. Heck, the gods have multiple aspects & avatars, right? So you can have your cake & eat it too.
Of the Dominions presented in this book, I have to admit I'm impressed. Arvandor, the fey-heaven of Corellon & Sehanine (the latter of which I like as mirror-imaged with Lolth-- white & black, black & white) has a "Great Hunt" in their realm that makes cosmological sense & presents a good-aligned afterlife for those who don't want to be bored. Mount Celestia is scads better in 4e than previous editions-- whereas in earlier version is was sort of a generic "heaven" with no challenges or story potential, devoting it to Moradin, Bahamut & Kord make it a primal & elemental (but not Primal or Elemental!) sort of Olympus. The mountains crackling with lightning, surging with dragon breath, smiths under the hills forging terrible weapons; oh heck yeah I'm down. Chernoggar is the best parts of the Blood War & the eternal strife in Acheron recycled, Bane & Gruumsh going at it hammer & tongs. Hestavar has a boring name, but is a place where you can put the "heaven in the clouds" motif, & for that I'm content. Erathis, Pelor, & Ioun all live here, which is an odd mix; two unaligned gods & the goodest of the Good. I'm interested; there are a couple of hooks here but not quite...enough. Add some cloud giants into the mix, maybe. Asmodeus' Nine Hells are; well, the thing you can say about this is "don't fix what ain't broken." The Nine Hells are the Nine Hells we're all familiar with. Don't mess with a good thing, or in this case, an evil thing. Tytherion is another Dominion lacking an evocative name, but the land of serpent haunted ziggurats devoted to Zehir & dragon-gnawed caverns devoted to Tiamat is pretty great. It seems more like a good campaign setting than an afterlife; that is my only concern. The rest of the Dominions-- the shattered, broken ones & the abandoned ones-- are great too; Carceri is as prisony & swampy as it should be, & uses the "abominations" well, the giant golden statue of Erishani is totally sweet & totally epic. You've got Pandemonium & a planar gladiator pit, & some other stuff for good measure.
Just for fun, The Plane Above throws in a bucket load of more flavor. They make the coatls actually useful; they've always been pretty, but now you can actually do something with them in your game (besides just make them less-Western dragons, like I always did). The Githyanki are great; I think 4e has really positioned them well, & since they are uniquely DnD, I think they should keep running with that ball. The Maruts are still less interesting than the Inevitables or the older editions plane of Mechanus, but slowly they are bringing them closer to both of those things, with clockwork castles & such. That is the direction they should rush to embrace. I don't care about the quom; they just...aren't. I like that they are dwarf-sized, but pastel guys with two faces just aren't doing it for me...though having them ride around on comets comes closest to reeling me in. Speaking of that; Astral ships! Someone said that they thought The Plane Above was Fourth Edition's Spelljammer. Well, no, but hellships of Asmodeus & lightning-shrouded Celestial ships are sweet in their own right-- & hey, rules for actually using them! Monsters, too; but like I said, since I don't Dungeon Master any Dungeons & Dragons games, that isn't so much helpful to me. Though I've always had a sweet spot for hecatonchires, & the "Banesworn" guy's shadow is neat, too.