It should actually be obvious from almost the beginning that this trilogy is about the way of the rose, since the other two Everien artifacts that were retrieved, came from the Way of the Sun and the Way of the Eye, leaving only the rose left unexplored. And, in fact, there is the poem at the beginning of The Company of Glass by Rainer Maria Rilke, easy to overlook, but obvious in hindsight. More than that, it is about Jaya, the living rose: (you may want to skip the quote as it might be spoilerific)
Then, at length, I realized that I held a shard that was silent. Utterly silent. What was wrong with this one? There was blood on it. I brought it close to my face and touched it with my lips. Very faintly, I could hear my own voice.
"I am Jaya, the Innocent Eye, the Invisible Flower. I am the Guardian of the Ineffable. My function is to See and Know and so become Wise. I am not an amalgam. I am one person, and I have been created for this purpose. ..."
If that doesn't give you chills about fate, I don't know what will.
This story, in short, is wild and involves all sorts of temporal paradoxes and science gone mad, hidden behind a thick veneer of fantasy. It reminds me of Gene Wolfe's Book of the New Sun with the complexity of the plot and the games played with time and the way science is, even more than in Wolfe's book, something very like magic. It also reminds me of Zelazny's Donnerjack, with the real world and the Liminal space where unrealized ideas, the trapped Knowledge of the Everiens, is trapped but can become realized, brought into actual being.
So, I suppose I should mention some downsides. While this is a fantastic story, the telling is not so great. Sometimes scenes about characters you don't really care about drag on and on when all you want to do is find out what happens to Jaya, Tarquin, Kere, and Liaku (Tarquin might not be that interesting in himself, but he is the character you feel you've been with the longest, since he is there from the very beginning.) The sex is mostly superfluous and thankfully, not much present by the time you get to the third book. Jaya steals the scene whenever she shows up to narrate in the first person, which is not a bad thing in itself, but since she is the only character to do so, it becomes quickly obvious that she's very important to the plot, especially in the third book when she starts getting her own chapters. (Spoiler: In the second her narration was mediated through Impressionists and seemed almost as if it might have been a recording or echo of the past, up until near the end when it became apparent that she was communicating from another place. END SPOILER.) Some things are never really resolved: What happened to the objects the Blackness swallowed? When did Jaya become real? What artifact was supposed to be found in the Way of the Rose? Who was Jaya's father? What made Hanji open up Jai Khalar to the invaders?
We are told that Jaya means Rose in the ancient language, but not much else about said language. What does Jai Khalar mean? Jai Pendu? Are there other names I've forgotten? What about the Animal Magic, which doesn't ever seem to appear in the story, even though it's mentioned over and over?
I guess that's enough questions to perhaps hint at the story. Have fun.