On Writing and Writing. A fabulous collection of mild-dystopia, SF evangelism, and good old snarky letters.
Stephen King's "On Writing" is generally seen as one of the most popular books on the craft by a popular author. Wolfe's 1992 "Castle of Days" should be right up there. It combines Wolfe's 1981 story collection "Book of Days" and 1982's essay collection "The Castle of the Otter" along with additional essays on writing and writers, and it's wonderful
First off, "Book of Days" is a fabulous collection of short stories centered around popular (primarily American) national holidays like Armed Forces Day, Arbor Day, Memorial Day, etc. Other, more universal holidays (Valentine's Day, Xmas, Xmas Eve) have entries as well, but it's mostly American holidays here.
While these national holidays serve as a sort of binding agent for American society, Wolfe's stories show an America that is coming apart at the seams....whether it's rationalizing neo-corporate slavery in "How the Whip Comes Back" (for Lincoln's Birthday), fleeing up into the trees as secret police descend upon your town in "Paul's Treehouse" (Arbor Day) or describing how people won't donate money to save endangered flora/fauna, but they might pay money to destroy it in "Beautyland" (Earth Day) -- the tales here present inventive, sometimes plausible, but consistently show a society that has lost its way in ways big and small (the computer aided matchmaking described in "Of Relays and Roses" (Valentine's Day) that's the subject of a Congressional inquiry is particularly quaint in hindsight).
"The Castle of the Otter" is a similarly rewarding, but for very different reasons, collection of essays about how Wolfe came to write his opus, "The Book of the New Sun" -- the essays largely occur between the 3d and 4th volumes and cover everything from his influences, definitions of some of his more esoteric vocabulary choices, and a fun little collection of novel characters telling their versions of jokes (it's as weird as it sounds).
Rounding out "Castle of Days" is a series of essays/letters/convention speeches by Wolfe on everything from authors he admires, trends he abhors, and several full-throated defenses of SF/Fantasy (or "fantastical literature") as a genre of literature deserving and DEMANDING respect (and study). Most of these defenses come in the form of convention speeches. With the popularity and nigh-ubiquity of cosplayers at events like ComiCon and the like -- reading about hyper-niche SF **book** conventions in the early 1980s is simply adorable
Anachronisms aside, "Castle of Days" might be among my favorite Wolfe collections -- primarily because of its non-fiction components -- where we finally get a glimpse of the (friendly, sarcastic, passionate) sheep in Wolfe's clothing.