March Books 4) The War of the Ring, by J.R.R. Tolkien
More in-depth analysis of the story of how The Lord of the Rings was written. We start at Helm's Deep, and follow through the end of Book III and Book IV (ie most of The Two Towers and then all of Book V (first half of The Return of the King). Tolkien's biggest problem was getting the chronology to work between four separated groups of protagonists so that they would eventually end up in the same place at the same time; placing the Paths of the Dead smoothly in the narrative was a challenge as well - it's probably the longest single flashback sequence in a book that generally avoids them.
The process of typing up the Helm's Deep / Isengard chapters of The Two Towers seems to have lost a few sentences from Tolkien's manuscript - none crucial but it seems to me that a "definitive" edition of LotR should be published which would at least include them in footnotes.
Finally, I was amused to see that the last person mentioned in the preface by Christopher Tolkien, thanking him for explaining an English folk-song reference, is one Mr. Neil Gaiman.