I think I'm running out of superlatives to describe this series, so I'll describe Winter's Heart as "very good''.
The major plotline is the attempt by Rand al'Thor, aided by Nynaeve, to cleanse the taint in saidin. Aes Sedai politicking and meddling continue, Elayne sets about securing her throne, and there's little mention of Perrin, while Mat Cauthon eventually meets the Daughter of the Nine Moons.
I would give a year of my life to spend a day in the world of the Wheel of Time. While Malazan is merely vast in setting and Sword of Truth sacrifices almost all else for top-notch character development, WoT seems to combine both elements plus more and then magnify it a hundred times. It's just too vast to take in completely.
The book starts out slowly, as with most books in this series, and then suddenly bursts to life in the final third or so. Despite this, there are quite a number of things to enjoy before the climax: the events leading up to Mat's discovery of the woman prophecy foretold he would marry, and Rand's bonding by all three of Aviendha, Elayne and Min.
Several things make this particular story stand out from the entire series. First is the relationship between the characters. The main characters are beginning to somewhat understand each other, unlike the endless bickering in the previous books. Rand seems to have realised he cannot defeat the Dark One without Aes Sedai help.
Second, the magic system reaches new heights. Most WoT fans do not give the magic as much credit as it should. It's incredibly well-structured for its somewhat casual use.
Also, the character development has reached a level where readers can actually identify characters by their speech, mannerisms and actions. It's the height of realism.
It's a great book with a blockbuster ending that will leave every reader wanting more.
