1. Nick Gevers, "Five Steps towards Briah: Gene Wolfe’s The Book of the Long Sun," http://www.ultan.org.uk/five-steps-towards-briah/
Gevers's treatment of The Book of the Long Sun is absolutely fascinating, and definitely worth reading by anyone who has read the tetralogy. He begins by observing some parallels between The Book of the Long Sun and Wolfe's earlier Book of the New Sun, but soon launches into a great analysis of the interaction between "the religious and the worldly," or faith and materialism, in Long Sun. He discusses the text in terms of plot, characterisation, and dialogue.
I was most fascinated by Gevers's assertion that each of the four books of Long Sun tends towards a different literary genre, and in doing so represents a scientific or secular approach to the problems afflicting the Whorl. Thus, Nightside of the Long Sun is seen as a detective novel; Lake of the Long Sun is read as a spy or espionage tale; Calde of the Long Sun represents the military story; and Exodus of the Long Sun embodies utopian idealism. Each of these secular attempts at problem solving and truth-finding turns out to be futile, and only manages to make things worse. Thus, as each of the secular approaches is tried and fails, only one option remains: that of "religious transcendence". Gevers explains how Wolfe, in demonstrating the futility of more 'scientific' approaches, leaves the acceptance of a "religious paradigm" as the only option.
2. Nick Gevers, "The Reader as Augur: Beginnings and Endings in Gene Wolfe’s The Book of the Long Sun," http://www.ultan.org.uk/the-reader-as-augur/
This article is more or less a continuation from "Five Steps towards Briah," and similar themes are addressed. In this article, Gevers's central thesis is that Wolfe uses augury (divination from the entrails of sacrificed animals) as an analogy for reading. Thus, in Wolfe's descriptions of Patera Silk's augury and (at the start of Nightside) textual interpretation, we have demonstrations of the kind of careful reading necessary to truly understand Wolfe's text. Gevers goes on to illustrate how careful readings of the beginnings and endings of the four books reveal to us how each of the books are to be read and understood. The article mostly comprises rich textual analysis, and of particular interest are his discussions of Silk's enlightenment at the start of Nightside, and the role of Horn, one of Silk's pupils, in the series.
3. Christopher Beiting, "The Divine Irruption in Gene Wolfe’s The Book of the Long Sun," Logos 11, no. 3 (2008). Accessed through the Project MUSE database.
Beiting's article, published in the Catholic journal Logos, is a very enjoyable read, and contains many insights into the religious themes of Long Sun. Beiting sees the story as one of "divine irruption" - the direct intervention of God in human history. This irruption comes in the form of Silk's enlightenment, which guides all the events which follow. Beiting makes a point of the fact that Silk continually misinterprets the Outsider's (i.e. God's) command - when told to "save the manteion", Silk assumes that the physical building is what must be saved, but only realises at the end of the books that the manteion is in fact the people of his quarter, who must be saved from the dying generational ship which is the Whorl. In this way, Beiting likens Silk to Saint Francis of Assisi, who was also commanded by God to "go and rebuild My house which, as you see, is being destroyed" (p. 86), and also misunderstood the command.
Beiting covers much of the same ground as Gevers, but makes another point which I found very fascinating: while Wolfe uses the common science-fictional motif of a generational spaceship, he offers a very new take on it. In the usual tale, characterised by Robert Heinlein's "Universe" (1941) and Brian Aldiss's Non-Stop (1958), the generational ship is failing (or is adrift, or has reached its destination) and the ship's inhabitants have, after many generations, forgotten about the universe beyond the ship and mythologised the ship's original builders, often forming a religion around this mythology. The protagonist of the tale discovers that their 'world' is only a spaceship, and must enlighten others to this fact, and encourage them to repair the ship or leave to colonise a planet. Beiting sees this usual playing-out of events as a "materialist allegory: the scales fall from the eyes of the ignorant, benighted protagonists, who abandon their primitive beliefs for the truth of a glorified Science and a bright, technological future" (p. 88). He argues that Wolfe is "demolishing this trope utterly" by using the generation ship paradigm as the foundation for a "Christian allegory" (pp. 88, 102). This article is definitely worth reading, if you can get your hands on it.