Particularly in an age where fluid movement and colorful palettes are some of the main characteristics of a praised or popular show, we are just not used to an anime that is visually told the way Fantascope Tylostoma is: highly stylized monochrome paintings accompanied by narration. I don't think a modern viewer can be entirely blamed for finding something like this OVA "boring" or just "weird". To some, that will be the nail in the coffin. But others might be willing to give it a try, and embrace this unusual journey.
This story uses the narrative device of "Story within a story". The narrator tells us the myth of the immortal Man who appears every 700 years, and the mysterious Man tells a joyful prostitute he meets his own story of how he came to be that way. There is some interesting playing of this device, but I will not spoil it for you. The meaning of the title is the first thing explained, and is a thread all too interesting to follow; I was immediately intrigued and this feeling remained for the entirety of the episode. As perhaps it's expected from an experimental movie so tied to its visuals, not every character action and not every thought is clear. The narration functions as a fine anchor and although its presence is a tad excessive sometimes, its existence is thoroughly justified: Fantascope feels very much like a tale, told verbally to you by someone else.
As for the characters. As I want this to be a spoiler-free review, I'll try being brief about this point. The (few) characters are appropriate for the setting they're in, and I think they're well-done for such a short story. The Man is a jaded and taciturn person, but he also doesn't shy away from telling his story, and to share his past actions (not all sympathetic, by the way). It would've been easy to have him be a distant, alien-like voyager, and I thought interesting that he's a more approachable protagonist and generous narrator than one might think. The prostitute who takes an interest in The Man is a charming character, and has some great lines of dialogue and an interesting form of enunciation that I talk more about below. The Goddess in the Cave is what you expect from a divine character: uncanny, passionate, and hard to fully grasp.
There isn't much in the way of character development, not only because of the running time, but also due to the very nature of this being a "legend" of sorts; in those, the tale and setting tend to override the characters and their psychological aspect.
The art is an imperative aspect of Fantascope, and any other artist would make of this an entirely different thing. Liking an art style or not is of course subjective, but Yoshitaka Amano's flowy lines and his ghostly, otherworldly characters so perfectly fit the post-apocalyptic and wavering gray setting, that it's hard to dispute its efficiency in introducing us to this world and the characters in it. The subtle movement of hair and water in static scenes were some of my favorite details to catch while watching the episode.
Another interesting point that I mentioned by passing above is the voice acting. I do not know if this was an artistic choice or a matter of budget, but the characters' voices in this OVA don't seem to come from trained or experienced voice actors; they feel bare, like real people talking. It's something I've seen used in "down to earth" anime movies (the adult segments of Ghibli's Only Yesterday come to mind), but in fantasy is rarer. It's a positive stand-out in my opinion, and it adds to the aura of mystery and unorthodoxy.
Honestly, I too was expecting no more than 30 mins of an out-of-my-comfort-zone experience, and was ready for a healthy amount of boredom, but Fantascope was actually quite enthralling to me. I'm not sure if it's a gem of storytelling or a must-watch for obscure OVA's. It's a fairly simple story (with its layers of complexity being open for interpretation), but it competently sets its atmosphere and aesthetic and maintains it firmly to the end. It'll probably give you, at least, an interesting half hour of entertainment.
