This book (yes I know that link is for the whole trilogy condensed into one book whereas this post is only going to talk about the first half of the Return of the King, but deal with it mate) is the fifth instalment of J. R. R. Tolkien's classic (virtually myth-status) fantastical trilogy. I have a lot to say about this trilogy, but I'm reading it all in one go, so I'm saving my reflections and my recommendations until the final post, and here will simply outline in brief the specific plot of this instalment. Spoilers, obviously.
Gandalf arrives with Pippin at Minas Tirith, the capital of Gondor, where they try to warn the steward Denethor (as Gondor hasn't had a king for ages) of impending dangers. Meanwhile, the Rohirrim (as in the cavalry of Rohan) are mustering for war, including Merry and Theoden's badass niece Eowyn; but Aragorn, Legolas and Gimli have gone off on a side-quest to try to persuade a bunch of ghosts to fight alongside them, which the ghosts agree to because SURPRISE yep you guessed it Aragorn is the rightful King of Gondor and therefore the only person who can command the ghosts' loyalty. Back in Gondor things are bad; orcs and their allies are pouring out of Mordor and laying siege to the defences - fortunately the Rohirrim arrive in time to make a big difference to the climactic battle on the fields surrounding Minas Tirith, and when the defeat of the good guys hangs in the balance, Aragorn turns up with his army of ghosts, who win the day. Faramir and Eowyn (the latter of whom, with Merry's help, had in fact killed the leader of Sauron's wraiths) have both been wounded, and Denethor (assuming Faramir [his son] to be dead and knowing that Boromir [his other son] is actually dead too) tries to burn Faramir on a funeral pyre - fortunately Pippin intervenes, saving the life of the steward-in-waiting. Aragorn uses his skills as a healer to bring Eowyn and Faramir back to full health, and then an intense debate ensues about what to do next about Mordor - where it is finally decided that the remainders of Gondor's and Rohan's armies will ride right up to Mordor's gates, to draw out all the orcs within so that Frodo & Sam have a clear run to the volcano where they must destroy the ring. Unsurprisingly this turns out to be quite a big battle.
But that's where this penultimate instalment ends...