In Xanadu did Kubla Khan
A stately pleasure-dome decree :
Where Alph, the sacred river, ran
Through caverns measureless to man
Down to a sunless sea.
So twice five miles of fertile ground
With walls and towers were girdled round :
And there were gardens bright with sinuous rills,
Where blossomed many an incense-bearing tree ;
And here were forests ancient as the hills,
Enfolding sunny spots of greenery.
But oh ! that deep romantic chasm which slanted
Down the green hill athwart a cedarn cover !
A savage place ! as holy and enchanted
As e'er beneath a waning moon was haunted
By woman wailing for her demon-lover !
And from this chasm, with ceaseless turmoil seething,
As if this earth in fast thick pants were breathing,
A mighty fountain momently was forced :
Amid whose swift half-intermitted burst
Huge fragments vaulted like rebounding hail,
Or chaffy grain beneath the thresher's flail :
And 'mid these dancing rocks at once and ever
It flung up momently the sacred river.
Five miles meandering with a mazy motion
Through wood and dale the sacred river ran,
Then reached the caverns measureless to man,
And sank in tumult to a lifeless ocean :
And 'mid this tumult Kubla heard from far
Ancestral voices prophesying war !
The shadow of the dome of pleasure
Floated midway on the waves ;
Where was heard the mingled measure
From the fountain and the caves.
It was a miracle of rare device,
A sunny pleasure-dome with caves of ice !
A damsel with a dulcimer
In a vision once I saw :
It was an Abyssinian maid,
And on her dulcimer she played,
Singing of Mount Abora.
Could I revive within me
Her symphony and song,
To such a deep delight 'twould win me,
That with music loud and long,
I would build that dome in air,
That sunny dome ! those caves of ice !
And all who heard should see them there,
And all should cry, Beware ! Beware !
His flashing eyes, his floating hair !
Weave a circle round him thrice,
And close your eyes with holy dread,
For he on honey-dew hath fed,
And drunk the milk of Paradise.

The most detailed and comprehensive study of Kubla Khan is in the remarkably detailed work, A Coleridge Companion, by the late, and dearly missed, scholar John Spencer Hill.

Here are a few excerpts from the book:

Kubla Khan is a fascinating and exasperating poem. Almost everyone has read it, almost everyone has been charmed by its magic, almost everyone thinks he knows what it is about -- and almost everyone, it seems, has felt impelled to write about it. It must surely be true that no poem of comparable length in English or any other language has been the subject of so much critical commentary. Its fifty-four lines have spawned thousands of pages of discussion and analysis. Kubla Khan is the sole or a major subject in five book-length studies; close to 150 articles and book-chapters have been devoted exclusively to it; and brief notes and incidental comments on it are without number. Despite this deluge, however, there is no critical unanimity and very little agreement on a number of important issues connected with the poem: its date of composition, its "meaning", its sources in Coleridge's reading and observation of nature, its structural integrity (i.e. fragment versus complete poem), and its relationship to the Preface by which Coleridge introduced it on its first publication in 1816...

... In a moment of rash optimism a notable scholar once began an essay by declaring that "We now know almost everything about Coleridge's Kubla Khan except what the poem is about". The truth of the matter, however, is that we know almost nothing conclusive about Kubla Khan, including what it is about.This flower plucked in Paradise (or on Parnassus) and handed down to us by Coleridge is, indeed, a miracle of rare device; but like all miracles it is largely elusive...

... By far the most intriguing question about this most intriguing of poems is "What does it mean?" -- if, indeed, it has or was ever intended to have any particular meaning. For the overwhelming majority of Coleridge's contemporaries, Kubla Khan seemed (as Lamb foresaw) to be no better than nonsense, and they dismissed it contemptuously.   "The poem itself is below criticism", declared the anonymous reviewer in the Monthly Review (Jan 1817); and Thomas Moore, writing in the Edinburgh Review (Sep 1816), tartly asserted that "the thing now before us, is utterly destitute of value" and he defied "any man to point out a passage of poetical merit" in it...

... While derisive asperity of this sort is the common fare of most of the early reviews, there are, nevertheless, contemporary readers whose response is both sympathetic and positive -- even though they value the poem for its rich and bewitching suggestiveness rather than for any discernible "meaning" that it might possess. Charles Lamb, for example, speaks fondly of hearing Coleridge recite Kubla Khan "so enchantingly that it irradiates & brings  heaven & Elysian bowers into my parlour while he sings or says it"; and Leigh Hunt turns hopefully to analogies in music and painting in an effort to describe the poem's haunting but indefinable effect:

"Kubla Khan is a voice and a vision, an everlasting tune in our mouths, a dream fit for Cambuscan and all his poets, a dance of pictures such as Giotto or Cimabue, revived and re-inspired, would have made for a Storie of Old Tartarie, a piece of the invisible world made visible by a sun at midnight and sliding before our eyes."...

... Throughout the nineteenth century and during the first quarter of the twentieth century Kubla Khan was considered, almost universally, to be a poem in which sound overwhelms sense. With a few exceptions (such as Lamb and Leigh Hunt), Romantic critics -- accustomed to poetry of statement and antipathetic to any notion of ars gratia artis -- summarily dismissed Kubla Khan as a meaningless farrago of sonorous phrases beneath the notice of serious criticism. It only demonstrated, according to William Hazlitt, that "Mr Coleridge can write better nonsense verses than any man in England" -- and then he added, proleptically, "It is not a poem, but a musical composition"...

... For Victorian and Early Modern readers, on the other hand, Kubla Khan was a poem not below but beyond the reach of criticism, and they adopted (without the irony) Hazlitt's perception that it must properly be appreciated as verbalised music. "When it has been said", wrote Swinburne of Kubla Khan, "that such melodies were never heard, such dreams never dreamed, such speech never spoken, the chief thing remains unsaid, and unspeakable. There is a charm upon [this poem] which can only be felt in silent submission of wonder". Even John Livingston Lowes -- culpable, if ever anyone has been, of murdering to dissect -- insisted on the elusive magic of Coleridge's dream vision: "For Kubla Khan is as near enchantment, I suppose, as we are like to come in this dull world."   While one may track or attempt to track individual images to their sources, Kubla Khan as a whole remains utterly inexplicable --
a "dissolving phantasmagoria" of highly charged images whose streaming pageant is, in the final analysis, "as aimless as it is magnificent". The earth has bubbles as the water has, and this is of them...

... Generally speaking, however, the most popular view by far is that Kubla Khan is concerned with the poetic process itself.   "What is Kubla Khan about?   This is, or ought to be, an established fact of criticism:   Kubla Khan is a poem about poetry"...

... The dream of Xanadu itself is an inspired vision...  the artist's purpose is to capture such visions in words, but in attempting to do so he encounters two serious difficulties:   first, language is an inadequate medium that permits only an approximation of the visions it is used to record, and, second, the visions themselves, by the time the poet comes to set them down, have faded into the light of common day and must be reconstructed from memory.   Between the conception and the execution falls the shadow.... the vision of Kubla's Xanadu is replaced by that of a damsel singing of Mount Abora -- an experience more
auditory than visual and therefore less susceptible of description by mere words...

The first and, for over a hundred years, almost the only reader to insist on the intelligibility and coherence of Kubla Khan was Shelley's novel-writing friend, Thomas Love Peacock:   "there are", he declared in 1818, "very few specimens of lyrical poetry so plain, so consistent, so completely simplex et unum from first to last". Perhaps wisely, Peacock concluded his fragmentary essay with these words, thereby sparing himself the onerous task of explaining the consistency and meaning of so plain a poem as Kubla Khan.

I agree with Peacock.  To me, the meaning of the poem is obvious, and I believe would be obvious to anyone with the appropriate worldview. 

The other reviewers remind me of Existentialists.  Because the Existentialists cannot think of a meaning of life, they arrogantly claim that life is meaningless.  The reviewers can't conceive that anything could be over their heads.

In order to truly understand the meaning, one would be inestimably empowered by adopting the viewpoint, or worldview, presented in my book.  I therefore moved the exegesis, showing the wisdom and beauty of Coleridge's magnificent thesis, to the section, Book in Progress.