This post is aimed at people who have not read the Wheel of Time books, but have heard about it due to the news surrounding the upcoming TV show.
The Wheel of Time is a lengthy high-fantasy book series by Robert Jordan (though the last three were completed by Brandon Sanderson after Jordan died. Probably the easiest way to explain the importance of the Wheel of Time is to note that when A Game of Thrones was published in 1996, it carried a cover blurb recommendation from Robert Jordan, and that was a significant factor in my acquaintances deciding to read that series. The Wheel of Time was Game of Thrones before Game of Thrones dethroned it (sorry).
This is especially relevant because it's blatantly obvious that Amazon is making the Wheel of Time TV show to capitalize on the immense popularity of the Game of Thrones TV show. The comparisons go deeper than that, though. Both Jordan and Martin had (have) a really serious problem which I like to call Epic Fantasy Bloat. This is where the author keeps introducing more and more characters and plotlines until there is so much going on that each book barely advances the overall progress of the story. Martin nominally attempted to solve this problem by killing off major characters, but this was a failure - he still needed to split the events of A Feast for Crows and A Dance with Dragons into two volumes, even though they cover the same period of time. Likewise, the Wheel of Time's tenth (yes, tenth) book contains material which mostly overlaps the previous book. The fan outcry was so intense that Jordan promised to speed things up, which he did (though he died after the eleventh book).
The Wheel of Time book series was enormously popular, selling over 80 million total copies. Why? Similar reasons to Game of Thrones: it features a richly detailed secondary fantasy world with large amounts of political intrigue and action. That, however, is about where the comparisons end. Jordan was extremely long-winded even in comparison to Martin. Even in books where important things actually happened, he was in no hurry to get to them. I believe he was trying to follow in the footsteps of Tolkien, whose verbosity is legendary. Instead of attaining a dignified epic narrative, though, Jordan produced an infuriatingly languorous meander through his world. For fans (and believe it or not, I'm a fan), this is bearable because of the incredible depth and detail. If you think Game of Thrones is complex, it's got nothing on the Wheel of Time.
There are also a large number of people who stopped reading the series partway through, and it's important to understand why. Obviously, the slow pace is off-putting for many. The readers with insufficient tolerance for such usually stop after book one or three. Book two is also slightly repetitive of book one, so many people stop there. More importantly, though, Jordan's character portrayal varies from shallow to offensive, which is a significant problem that the writers of the TV show will need to deal with.
The world of the Wheel of Time is (at the start, at least) one where only a small group of women have magic. This leads to a gendered power imbalance that is politically and socially important, and the series dwells heavily on it. In addition, many of the early points of view are of teenaged boys and girls, who spend a lot of time angsting about each other, as teenagers do. Jordan, though, was 41 by the time the first book was published, and it shows. The really sad part is that he thought he was being progressive (Heinlein had the same issue, but that's a different essay). The series features a lot of strong female characters who have their own story arcs - it passes the Mako Mori test many times over. However, in any given moment the portrayal of any given woman is more likely to be caricature than character. One character was notorious for tugging on her braid when angry, and this was her defining characteristic until well into the series. Many of the women repeatedly cross their arms under their breasts when angry, usually at men. Later in the series, there are some problematic male-fantasy-centered story elements which I won't get into for spoiler reasons. What I'm saying is that while Jordan thought he was doing a great job of writing women, he wasn't. Compared to most of what came before him (including but hardly limited to Tolkien) he was downright fantastic, but even in the 90s when the first several books came out, his depictions ranged from cringy to offensive. Now, in the 2010s, those aspects of the books are unacceptable. The writers of the TV show will need to do better.
Even setting aside the gender issues, Jordan was frequently guilty of lazy plotting. There are many, large, world-altering sections of plot that could have been solved by characters communicating with each other. These characters had the means and motive to do so, but Jordan invented half-assed reasons for them not to so that the plot would continue moving in the direction he wanted. This is an unforgivable sin of writing.
The good news is that the TV show has a real opportunity to improve a series that is beloved by many. Just as the Game of Thrones TV show improved on the books by cutting out large parts of it (until, of course, they ran out of books and floundered), the Wheel of Time TV show can improve on the books by turning a long-winded slog into a tight, exciting narrative. Will they actually do this? I don't know. Will they go too far, and lose the depth of the books? That is unfortunately possible, as there are several recent examples of bad fantasy adaptations.