Three issues, three different narrative styles. Done poorly, this would highlight my "bad" section, but subpar execution just isn't Jeff Lemire's style. What is his style: distinctive stories, delivered in pleasantly unexpected ways.
The most compelling moments in a love story are often defined by its conflicts. "Nika and William meet and can communicate right away and live happily ever after" just doesn't have the same punch as "Nika and William met briefly, but were cast apart by space-time, and now they have to reconnect and also possibly save the universe." Lemire uses this device to his advantage, and throws us curveballs at just the right moments to keep the pacing up and make the story of their relationship interesting.
Also interesting: things that are left mysterious. Scenes that are fragmented, or in need of translation from alien dialect, leave us to fill in pieces of the story with our imaginations, and (again with the caveat of "when done well..."), make it that much easier to invest in the characters and their stories. Because we're trying to solve their mysteries, and keep them safe from impending doom (by working out possible ways that everything could still turn out ok), we enjoy guessing why Lemire called out the syringe in Nika's cell and how she might use it in a few panels, or trying to translate alien speech to predict whether the Earthlab outpost will survive.
Locking it all together is a very solid, very self-aware big-picture story. We know that TRILLIUM wraps in eight issues, and we can also see that the series is paced to reveal just enough in each issue to keep us satisfied until the next. We keep gaining context about the world(s) we're peeking into -- including the imminent end of the Earthlab humans due to military/political stubbornness in the face of scientific evidence that goes "off-plan."
Lemire makes a stylistic choice with William's pages that is completely in-tune with the disconnection Nika and William are feeling, but it's one that sacrifices practicality in favor of artistic merit. All of William's pages are upside-down; for print readers, this is mildly inconvenient, but for digital readers, who are advised that "This page is intentionally inverted to match how it appears in the print edition," there's no choice but to try reading upside-down or awkwardly position around one's device to try circumventing auto-rotation.
TRILLIUM continues to shine as one of Vertigo's gems; it's unique, it's beautiful, and it's compelling to no end. It's incredibly easy to become invested, not only in the fates of Nika and William, but of the universe at large. This kind of immersion is Lemire's wheelhouse; in just a few issues, he's built a world (or two, rather) that begs to be cared about, and seeded a love story that transcends time and space.