Three-fourths of “The Dark Tower VII: The Dark Tower” is great.

Perfect, one might say. Answers are given to those whose lives were completely interrupted by the release of the book. Battles are fought against tyranny and evil that thrill even the most casual reader. And, yes, a few of the main characters, people whom Stephen King had used to take the reader across five other volumes, enter “the clearing at the end of the path” (this is how King’s characters describe death).

But damn if that last quarter isn’t bad.

No, it’s not terrible per se. There’s still the required final showdown between our hero, Roland, and the bottomlessly evil Crimson King. And, yes, eventually we do get to climb the tower that King’s fans have been speculating about for decades.

But it’s all about consistency. The bulk of the “Dark Tower” books, a personal favorite still being number two, “The Drawing of the Three,” are richly imagined and written with the grace and fluidity of a poet, sometimes. There are those chunks here and there where King writes about farts and boogers, which seem out of place and shockingly juvenile. This is true with the bulk of “Dark Tower VII” as well.

But toward the end, the reader will get the feeling he is holding a copy of King’s first draft, not the final manuscript of what is widely regarded to be his most substantial work.

There are reasons for this. King was reportedly hounded by deadlines, and had been doing revisions to the tone until the day it was shipped out. Of course, this is all rabid-fan hearsay, but the rough tone of the last section of the book tends to lend credence to it.

King envisioned “The Dark Tower” as his magnificent final opus, his answer to Tolkien’s “The Lord of the Rings,” and he has written at length about the youthful hubris that caused him to set out to write the world’s longest popular novel, (King contends that all the Dark Tower books comprise one long tale). And yes, to many extents, he has succeeded. The book is long, and chunks of it are clever and touching, which are rare feelings to experience when reading a popular novel.

But the tale, sadly, was oversold. King told his fans all his books were connected to the “Dark Tower” series, and for years, constant readers have been pouring over less-than-engrossing tomes like “Insomnia” and “Rose Madder,” searching for clues that would more clearly illustrate whatever fate King had in mind for his hero. But in the last book of his opus, these things seem forgotten, and the reader gets the distinct impression that he has been lied to.

It seems as though King, unable to make everything fit in the final pages, simply called himself a liar.

Perhaps the worst fault of the book comes near the climax, as King himself breaks in with an author’s note telling the reader that he or she shouldn’t read the last pages, because they would ultimately be disappointed by them. He comes back later to tell his faithful readership not to bother writing him about the book, and under no circumstances to stop by his house for a chat.

In the end, the “Dark Tower” is not a failure, and the faults are only as magnified as they are due to the scope and expectation that awaited it. But this, of course, was inevitable. King wrote a story so great, so grandiose and so epic, that in the end, even he failed to come up with a decent way to end it.