I've read it. If I recall correctly the protagonists (Joel, Finder and Holly) along with the antagonists (Miranda and a Banelich) first cross from the Forgotten Realms into the Outlands through a portal in the Dalelands (while aboard a busted up Spelljammer). They eventually ditch the spelljammer and use another portal to cross into to the planar city of Sigil. To arrive in the Astral Plane they hop through another portal; this one located in Sigil's Shattered Temple. That's a summary of the journey; sans all the convoluted plot developments.
To resurrect the dead god Miranda, a die hard cleric of his, teams up with (i.e. mindlessly serves) an evil Banelich which claims to embody the dead god's essence. Although neither of them know anything of the Outer Planes, the endeavour to journey there in search of an ancient relic of the dead god; the fabled Hand of Bane. With the plot-device in hand (heh heh) they plan to then journey to the god's corporeal remains in the astral plane to conduct a ceremony which will reunite Bane's body with the Banelich's essence and the power contained in the hand back together into one vile whole. Voila! Bane resurrected; And there will be much rejoicing.
There are many plot twists;
• The elderly mentor/priest that Joel travels with, Jedediah, turns out to be his own patron god Finder in a poorly executed disguise.
• Finder at first doesn't really care about helping or stopping the Banelich, he simply chases around after him in hopes of retrieving the half of the Finder's stone which the Banelich acquired early on and which contains some of Finder's divine essence. Joel has to lay a heavy guilt trip on his god to spur him into taking action against Bane.
• The hand of Bane turns out to be sealed up in a ancient shrine beneath a bookseller's shop in Sigil.
• The good guys end up with the Hand of Bane, but are made to trade it to the Banelich in exchange for it's half of the Finder's Stone and a hostage when everyone's back together on Bane's corpse in the Astral plane.
• At their moment of triumph, the Banelich blatantly shows his misogynistic contempt for Miranda and figuratively kicks her around like a puppy before attempting the final ceremony. But the ceremony fails because, as it turns out, only a living cleric of can do the deed. So the Banelich hands the Hand to Miranda and none too kindly orders her to perform the ceremony. The good guys talk her out of it by reminding her that she's evil and a cleric of the god of tyranny. With an evil gleam in her eye she gives the lich the finger and makes and break for it.
• Finder redeems himself by selflessly attacking the lich and risking his immortal essence to stop it from catching Miranda.
End result; all the good guys are alive and happy, Miranda flees, the Banelich is destroyed and Finder gets a truly devoted cleric who's nicer and wiser than he is. The end. That answer your questions?