Much of the text of this letter has been available in the form of Humphrey Carpenter’s abridgment of Tolkien’s draft of the letter.2
As part of the auction, RR Auction made available good-quality scans of all five pages of the letter, affording us the opportunity of reading the full text of Tolkien’s final (beautifully penned) draft for what I believe is the first time.
Pieter Collier at The Tolkien Library has republished the scans (as I have here, too), and has transcribed the letter in full. An ad hoc group of Tolkien scholars promptly submitted a number of corrections and suggestions, which Pieter immediately incorporated into his transcription. The result seems to be a highly accurate reading of Tolkien’s letter. Some highlights:
Maps take a lot of time and work. It would of course be impossible to make a map of an ‘invented’ tale, or rather to write a mappable tale, unless one started with a Map from the beginning. That I did — though inevitably some inconsistencies, needing the adjustment of map or text, crept in in the course of a long work, constantly interrupted. But there is a wide gap between a rough map, though accurate in scale and distances, and one drawn and lettered passably enough for reproduction!
You would, by the way, render us a very great service, if more and better maps are to be produced, if you would be so kind as to send us any notes of faults, inconsistencies, or omissions, in maps or text.