On History: Sabre
The story revolves around Sabre, a swashbuckling hero in a dystopian 2020. The tyrannical government has captured a group of rebels, and Sabre, along with his lover Siren, has to make his way through an abandoned amusement park to save them. Naturally, many of the rides have been turned into death traps which the two must escape from. After freeing the captives, Sabre eventually encounters the Overseer of the park and they fight to the death.
McGregor originally conceived of the idea as a weekly newspaper adventure serial. While the final story was written as a single graphic novel, the changing scenes as Sabre moves through the park call back other serial adventures like Barbarella and Modesty Blaise. The climax is decidedly bigger than a newspaper strip would allow, though, certainly, and there's a definite sense of closure that you don't typically get in a strip.
But what makes the book notable, with regard to its place in comic history, is that it was set up as the first direct market graphic novel. And to seemingly emphasize the point that this still-new direct market was something markedly different than newsstand distribution was the content of Sabre. In particular, Siren is shown naked and/or topless in a few scenes, and she and Sabre as expressly shown having sex. The sex act itself would obviously have been banned from newsstands, but that it was an interracial sex act probably would have caused a stir as well. While interracial couples certainly weren't unheard of in 1978, there was still a reasonable amount of pushback against the idea from certain quarters.
Compare Sabre against Dazzler #1, the first pamphlet comic book exclusive to the direct market. From a content perspective, Dazzler is effectively no different than anything else Marvel was producing around that time. Sabre wasn't pushing boundaries necessarily -- there had been plenty of Tijuana Bibles and underground comix depicting even more explicit sexual acts dating back to decades earlier -- but they helped establish the direct market as a respectable venue for 'mature content' comics distribution.
There's almost a direct line from Sabre to Watchmen and The Dark Knight Returns and, had Sabre (or something very much like it) not been published when it was, I think it would've been harder to see a lot of other now-classic material make it through the DC/Marvel pipelines.