Art: I like the cover art and the illustrations of the tower and mermaid. Everything seems a little haphazardly put together though, too many different styles of art that clash with each other... the cover photocollage, tablet frames, and lander illustration all look like they belong to different modules. The amount of yellow text on black is a bit hard on the eyes, as that combo is typically used for short, attention-getting warnings and not long blocks of text.
Writing: Decent overall. No particular complaints, but also nothing that strikes me as particularly memorable or evocative.
Game Design: This is set up like an adventure but structured more like a single encounter. There's one task and seemingly only one way to solve it, and one threat... there doesn't seem to be any way to avoid the siren or deal with her other than through combat, and with her stats and ability to enthrall players, there's a good chance this just ends in a quick TPK with bad rolling. Perhaps the way to go would have been to develop the monster and its mythology in greater detail and then just provide hooks for integrating it into a larger adventure? It feels like the monster is the point here, and the adventure is so minimalist that it's more constraining than additive.
Theme: Space mermaid is certainly ancient myth + Mothership. Maybe it would be more thematic if she'd hijacked the antenna to broadcast her call, rather than destroying it?
Layout: Nothing too crazy. Does the trick for the most part. The positioning of the boxes on the lander illustration is kinda scattered and not visually appealing. It seems redundant to have components listed overtop of the image and then a separate box underneath describing the lander. I would rethink how you're presenting this info: either a longer column of text and then an image without stuff on top of it, or a larger image with tidier, more helpful labeling and maybe a shorter overview in the corner or underneath.
Utility: I think the adventure is too minimal and the threat level of the siren too high to be used without some additional contingency planning by the Warden. Otherwise, there's a good chance that the game lasts ten minutes because the players have no choice but to leave the lander, whereupon they fail some rolls and are all dead or enthralled before they've really done anything.
Favorability: I like the monster, and thought about doing something with sirens myself. But I'd be more likely to drop her into something else than to run this specific scenario.