It is tough to think of a modern novelist who more richly merits the epithet "asshole" than Evelyn Waugh. That said, in my 20s I was one of those fans you describe. I never went as far as carrying around a teddy bear, as did one Brideshead Revisited epigone of my acquaintance. But to read Waugh in the 1980s—after having been educated mostly by people who thought literature was "great" to the extent that it prefigured the prejudices of Ivy League faculties of the time—was exhilarating. The more "reactionary" Waugh got, the more liberating it felt to read him. And I ran through pretty much all of his novels in my early 20s.
There is nothing like reading a Waugh biography (I've read the Stannard and the Sykes) to make his "courage" look like toadying to whichever family of Catholic dukes he sought to please, or his "satire" look like petulance. I don't particularly like Waugh now, even if it makes me feel like an old man to say so.
Why were these novels—two representative ones from mid-career, and two outliers from his dotage—"mysteriously grouped together," as you put it? My first guess was that it was an unobtrusive way of smuggling Black Mischief off the politically incorrect index and into print. The introduction by Ann Pasternak Slater confirms this suspicion. It is the very worst kind introduction, cosseting the reader, insisting that he not embark on the novel until some pedant has given away the plot, supplied him with a map of all the Deep Symbolism, and leeched away any joy of discovery with Master's thesis–level chatter. ("Transposition and cross-over recur throughout the novel. ... Misunderstandings and metatheses sustain the mode. ... The game of pingpong's instant reversibility—its high-speed ricochet, a to-and-fro getting nowhere—epitomizes the novel's elaborately inconclusive narrative structure.")
A larger problem is the way Ms. Slater tries to obscure Waugh's deeply felt (if always jolly) racism. She rests her case on a thin reed: the particular sleaziness of the thieving Englishman Basil Seal. "It is one of the novel's many ironies," she writes, "that Basil is ... the final embodiment of extreme barbarism. ..." Both blacks and whites are disreputable, but "the main difference is the incalculable antiquity and occasional dignity of the African culture, and the mindless infantilism of the Europeans." Waugh is not blind to the ways decadence can become indistinguishable from barbarism, but you really need to tie yourself in political knots to give the laurels of savagery to anyone but the Azanians—"black, naked, anthropophagous," as Waugh describes them at one point.
Since you asked, I think Black Mischief and Scoop rank toward the top of his achievement; Pinfold may be my favorite book of his, for non-literary reasons I'll go into tomorrow; and The Loved One, his novella of courtship in the California funeral industry, is the work of a prematurely dissipated talent, easily his weakest book.
One gets the impression that this novel owes its reputation to the perfect convergence of its sensibility with that of 17-year-old malcontents, which is what most Americans are when they stop reading serious books. The Loved One is a "romp," that word critics use anytime an author they feel required to laud proves too inattentive to trim his plot down to intelligibility or lift his humor above barroom cracks. There is something hollowed-out about the jokes, as when the Englishman Dennis tries a vegetarian treat called a nut burger: "I've often wondered what they were," he says. "It is not so much their nastiness as their total absence of taste that shocks one." Ho ho ho! This has the form of the Wildean sally—which basically announces that the author thinks he's being funny—without the Wildean wit.
To be fair, I've always hated this novel. Dennis spends the whole book as a hapless, troubled, but ultimately decent person, before quite forthrightly declaring to the fragile Aimée Thanatogenos, who paints the faces of corpses at Whispering Glades cemetery, that he plans to sponge off her for the rest of his life, and ridiculing her when she demurs. It makes no sense, but it does the work of setting up Aimée's suicide, however lazily. Aimée is an arbitrary collection of points Waugh wants to make about America. She is the most doltish, unintrospective person imaginable, but when Waugh needs her to draw out a joke from Dennis she rises to docent-level intelligence ("I've seen painting there not ten years old that's completely lost tonality. Do you think anything can be a great art which is so impermanent?").
In satire, stick figures will often do. But where plausible characters are absent, they must be absent to some end. Waugh's point is that America, by worshipping the body, has turned its back on the belief systems that gave their European ancestors meaning. Leave aside that this reads decidedly oddly in 2003, when Europeans believe in European culture considerably less than Americans do. Even where Waugh is most eloquent in making it ("Which came first in this strange civilization, he wondered, the foot or the shoe, the leg or the nylon stocking? Or were these uniform elegant limbs, from the stocking-top down, marketed in one cellophane envelope at the neighborhood store."), this is a facile point, one that can be adequately handled by the Malvina Reynoldses of this world.