I must admit that I can't ever remember reading this before, but after watching 'Lewis' last night I thought I would see if there was a free copy on this site. There is another copy also in the kindle popular classics store, but I could only find one review for the kindle version, all the others being cross posted from tree book versions. That review indicated that there were problems with the text, so I decided to download this version instead.
As far as I am aware all of it is here with no problems as such, but of course as I am not familiar with this particular poem, others may pick up on mistakes, etc. I know that there are all sorts of theories and ideas surrounding this poem, including even if it was written for children, but I think that Lewis Carroll himself would have said that if you see something it it, then good, if you don't, then that's just as good as well.
Whether there is some sort of puzzle or other hidden meaning in this, then let people believe it is so, personally I see here a very funny nonsense poem that had me laughing out loud. After all, what is this about?, but a very unusual crew looking for something that they don't really know what it looks like. Improbable, impossible, and highly unlikely, this is a great poem to read.