First off, Stephen King is currently my favorite author, my favorite book being'Salem's Lot, and this is not only his longest singular work (his longest work is the Dark Tower series, of which I have read the first three out of seven) - it is the longest book I have read to date. According to Yahoo! Answers, it consists of 464,218 words. Both editions I read from (one was rain-soaked and I bought an older copy) had 1,141 pages. It is an awesome epic novel and I recommend it to the epic fantasy and/or horror fan.
After a deadly plague released by a government mistake sweeps across the world and wipes out ninety-something percent of the population, those who survived take two sides: the good guys flock to 108-year-old Mother Abagail in Colorado and the bad guys run to Las Vegas to Randall Flagg, a demon or devil of some sort who appears human but can both shape-shift and project his soul into animals. He gives off an aura of extreme, cold terror to Abagail's people, and eventually a few brave men decide to journey from Boulder, Colorado, to Vegas on foot to confront the dark man, as Flagg is often called...for the ultimate stand.
I really loved this book, but the climax, shall we say, was a bit of a deus ex machina. Meaning "God of the Machine." I don't want to give too much away, but I will say that God quite literally had a hand in things, where he could have helped the entire time. That is the same problem I had with C.S. Lewis and his Narnia books, which I need to read the rest of still: God reaches in and fixes things. The movie Avatar (the James Cameron one with blue people, not The Last Airbender) did this too: "Jake! Eywa heard you!!!"
But other than that, the writing was quite good. I was never quite sure who the main character was, but I don't think there really was one: Star Wars does that too. More of an "overall epic story" thing.
Final grade: B