The Two Towers (Book Three) by J.R.R. Tolkien

Book Three of The Lord of the Rings is Tolkien's masterpiece within a masterpiece. His achievement is remarkable. 

Frodo and Sam have surreptitiously left the Fellowship of the Ring; Boromir is slain, and Merry and Pippin have been abducted by orcs and taken westwards.  Aragorn, Legolas and Gimli must decide their course of action, and they choose to pursue the orcs, in the faint hope of recovering their lost friends.

And from this point Tolkien takes the reader from one end of the land of Rohan to the other.  Where in the previous volume the travellers crept or plodded with stealth across the countryside, they now run and ride openly, desperately and relentlessly in an ever-widening field of action.  We witness court intrigue, a battle and two sieges; and we are immersed even deeper into the history and geography of Middle-Earth.

But perhaps Tolkien's genius is nowhere more conspicuous than in the way he handles branching, overlapping and intertwining strands of narrative.  Friends are parted, reunited and then parted again.  We jump from place to place and from time to time as the story unwinds. Here, we witness the action as it unfolds; elsewhere, we have deeds reported to us in retrospect; the point of view shifts and then shifts again.

The book deals largely with friendships made in the midst of war, and with friendships broken by the thirst for power.  The healing of Theoden kindles a friendship where once there had been enmity; valor in arms in the face of a common foe unites Aragorn and Éomer, and deepens the friendship between Legolas and Gimli.  Merry and Pippin, already bonded to each other by their kinship, meet danger together; and they find a wholly unexpected friend in a wholly unexpected quarter.

As we draw closer to the midway point of the larger work, great deeds are done and are yet to be done.  Tolkien's familiar theme of hope versus despair is never far away.  At one point the White Rider says:

I have spoken words of hope. But only of hope. Hope is not victory.

No, deeds must play out; and one may win a battle and yet lose a war.  Book Three ends with the friends riding from a victory to what is likely to be their long defeat. 'Run now!' [cried the White Rider.] 'Hope is in speed!’