The Cross-Time Caper is legendary, often referred to as one of the most Pure Fun storylines of the Dark Age. And that reputation is well-deserved, though it's a very specific kind of fun - fun in the same way a late-80s fantasy movie is, the kind of weird stuff that you caught on TV once as a kid and still aren't quite sure if it was real or just something you dreamed.
In terms of plot, it's rather chaotic, which sometimes leads to the individual parts feeling a bit loose and disconnected. But this disconnect allows for experimentation - with genre, with format, and especially, with what happens to the characters.
There's an ongoing A-plot of Excalibur leaping uncontrollably from alternate universe to alternate universe, trying to get back home but getting caught in genre-specific shenanigans. Two of these are primarily fantasy stories, one is a parody of Marvel itself, and one is an anime homage (primarily Speed Racer and Dirty Pair - US anime fandom was pretty new at the time). This last ends up linking up to the ongoing B-plot - the crossdimensional mercenaries known as Technet being hired to rescue Jamie Braddock, Captain Britain's brother, who turns out to be not only an awful person, but an enormously powerful and immature reality warper. Yeesh.
The really deep engagement here is not just trying out different genres, but throwing known characters into these genres. Kitty Pryde, AKA Shadowcat, gets her personality manipulated to fit society's demands; Rachel Summers, Phoenix, gets to experience life without the blessing-slash-curse of her powers; Kurt Wagner, Nightcrawler, becomes a swashbuckling adventurer; Meggan, AKA Just Meggan, finds worlds that she fits in better than "home"; and Brian Braddock, Captain Britain, deals with the limitations of masculinity, nationality, and the superhero role. This is the meat of the story, this intersection of character and wildly-changing setting, and if that's the kind of thing you enjoy, these comics come highly recommended.