Let me deal with the bibliographic details first. There, I'm on firmer ground.
The first edition of 'The Black Corridor' (Ace p/b) got its typographical art (as Mike says, "words create a pattern of other letters forming other words") correct, but had the book's opening passages cut.
The first British edition (Mayflower p/b) got the book's opening passages correct, but messed up the typographical art.
Although messed up, the first British edition at least managed to get the various pieces of typographical art all on their correct pages, which is more than can be said for all subsequent American editions (such as the Ace h/c and the omnibus combining 'T.B.C.' with [bizarrely] 'The Adventures Of Una Persson And Catherine Cornelius' [sic]).
For the Orion and, particuarly, White Wolf omnibus editions of 'Sailing To The Future' (incl. 'T.B.C.'), every effort was made to perfect both the opening and the typographical art.
With regard to interpretation of the book, I think Mike's perfectly allowed NOT to be drawn on its meaning. It's one book, possibly more than any other of his, which is open completely to the interpretation of each reader. I've read it several times, and each time seem to see different layers of interpretation within it. I was quite young when I first read it, and took it completely literally, gleaning no underlying metaphor whatsoever. (In that, I think Mike's right in saying that it was aimed deliberately at an older readership.) Subsequent readings have led me to believe that very little in 'T.B.C.' can be taken at face value, even the Earth-bound segments. They're obviously coloured by (Cornelius?) Ryan's deranged recollections. I think there's little doubting that he's become unhinged, but