Remember the scene in The Parent Trap, where Lindsay Lohan's character surprises a table of adults by knowing how to drink wine like a connoisseur?
That's what reading The Two Towers is like.
If The Fellowship of the Ring was like fine wine, it was a fine wine that simply needed to age before it could be drunk by newbies and wine aficionados alike. The Two Towers, however, is like a fine wine that only aficionados really appreciate. If a newbie tries to take a sip, they're either going to love it or hate out, and they'll either swallow it or spit it back out into the cup.
While Tolkien's work in The Two Towers maintains the quality that was found in The Fellowship of the Ring, the difference between these two wines--pardon me, between these two books--is that The Fellowship of the Ring is, for the most part, a fast-paced adventure story ([spoiler] minus the ever long enemy of even the most dedicated Tolkien aficionados, "The Council of Elrond" [/spoiler])...and The Two Towers is not.
The Two Towers is a struggle for any character biased readers.
[spoiler] Frodo and Sam lovers, you have to wait until you're over half-way through this book before your beloved characters shine. [/spoiler] Tolkien branched away from traditional storytelling--or storytelling has branched away from tradition, whichever you prefer--by dividing this book into two parts, and only dealing with certain sets of characters in each part. [spoiler] You spend a fast-paced few chapters with Aragorn and Legolas and Gimli, and then suddenly you're reading "The Council of Elrond" all over again in the form of an enormous chapter called "Treebeard," and then you have some more fast-paced action, and then suddenly you're off with Frodo and Sam for the rest of the book... [/spoiler]
For readers who are accustomed to healthy doses of all characters throughout the course of a book, or for readers who have unhealthily particular fondnesses for certain characters, this makes The Two Towers a bit more of a slog.
So if you're not bothered by the two book, character separating, alternating style of Tolkien's writing, you should be good. Right?
Maybe. That's where the wine part comes in. If you're a wine aficionado, maybe you can just take a swig and still enjoy the wine. It's not going to taste as good as if you'd let it soak into your palate (or whatever wine aficionados do before drinking their beverage). But if you're new to fine wine and you just chug it down, you're faced with the two already named options: you'll love it and drink it...or you'll hate it, and you'll spit it out.
The Two Towers should be read like wine is drunk: with a refined palate, the way Lindsay Lohan does it in The Parent Trap. Except that this book will, in all likelihood, not leave you inclined to even pretend to be tipsy.