Disclaimer: reviewing uncorrected digital proof via NetGalley
"Adrift" is apt: the author took on a challenging format and offers some true excellence in character writing and worldbuilding, but the experience of reading this book is, for better or worse, as if you're just as adrift, confused, and purposeless as main character Hallie.
Hallie's doing the dissipated youth finding herself routine in Paris. But before we find that out, we have to wade through some future revolutionary setup with time-travellers who want to go back and change the past to resolve the blighted dystopian future they're living in. This is the frame story and the plot, but Hallie doesn't figure out where she fits into it until extremely late in the game. Instead, she's working and drinking her life away in a bar, hanging out with people who do the same, and - unwillingly at first - hopping through time in the cellar.
There's a lot to like at a technical level. Swift conveys that dreamy/nightmarish feeling and atmosphere of being 20-something and finding your group on the road, living in the moment, but with an uneasy awareness that the moment must pass and you're more than where you're stuck now. Paris and the group of international workers at Hallie's bar are conveyed with detailed world-building excellence, including what (as far as my limited French can tell) is accurate and characteristic uses of French.
If you think of this as a literary novel, it deserves a high rating. Dreamy, evocative, endlessly confusing, but in a way that hints at careful construction, it's an effective deep-dive into character. But the frame story plot lags as Hallie finds herself, and there are too many mysteries held for too long for it to be effective as a genre work. If you need fast, thriller pacing, spicy romance, or intricate and engage SFF goings-on to enjoy a book, this is not the story for you. If you're happy to invest some time, drift through the story, and maybe reminisce about (or look forward to) your own dissipated youthful travels, this offers much to appreciate. Just sit back and let it flow.