Olympos by Dan Simmons
The previous book, Ilium, began relatively simply. You had ancient Greeks and Trojans fighting the Trojan War (apparently taking place on Mars), watched over by 20th Century Iliad scholars (who had been reconstituted from their grave remains many centuries after their deaths by what appeared to be Olympian gods). The gods were using the scholars to determine if there were inconsistencies between the War and its description in the Iliad. We then learned the gods were actually using advanced technologies to carry out their "divine powers". We were also introduced to part-organic / part-machine intelligent beings working in the asteroid belt and on moons further out in the solar system - who had become concerned by the vast quantum activity around Mars. We also saw the small number of "old style" humans remaining on Earth who had lives of leisure; taking advantage of, but not understanding, the technology underlying their lives.
Things aren't quite so simple in Olympos. [Actually, these trends started towards the end of Ilium.] Achilles and Hector have been tricked into joining forces for a joint Greek-Trojan war against the gods and they've been joined by the cyborgs from the outer system. We're told the Greeks and Trojan have not been battling on Mars, but it only seemed so because there is a quantum tunnel linking the future Mars to the ancient Earth. We're told the gods' powers are not their own technology, but from some unknown beings from outside our solar system, and the source of the quantum activity used by the gods is on non-ancient Earth.
We find the book hopping back and forth between subplots - some of which branch-off new subplots.
* The beings that have been acting as servants for leisure-life Earth humans stop waiting on the humans and then start attacking them.
* Players in events include an AI entity that appears holographically as Prospero, a human-shaped but internally very different being called Ariel and a woman who is a "post-human". These characters try to influence the direction of some human characters, but sometimes they go to a lot of trouble to accomplish no clear objective.
* An alien being, Setebos, has come to Earth to feed on some attribute that remains in places where atrocities were committed. Caliban serves him, as well as a host of similar creatures referred to as calibani.
* A spaceship flown by the cyborgs tries to bring Odysseus to the future Earth, but receives radio messages demanding they bring him to an asteroid orbiting Earth.
* We find that the "old style" humans have been designed with a variety of functions they can carry out via their ability to interact directly with a super network - if they know how.
* One of the gods causes Achilles to be helplessly in love with an Amazon he has killed in battle. He sets off to Olympus to have her restored to life.
* More gods than just the Olympians get involved.
There's more, but some examples might involve more spoilers. And that should give you and idea.
In Olympos, we hear less about Proust and Shakespeare's sonnets. And the subplots about the Greeks, Trojans and gods have less in common with the Iliad. However, there are many allusions to Shakespeare's The Tempest, and numerous other literary elements.
... There are certainly "interesting" last scenes for Achilles and Odysseus.
Olympos (and Ilium) are what more literary types like to refer to as "ambitious". There's a lot to them and Simmons works to incorporate parts of Homer, Shakespeare, Proust, etc. into it. It's not my intention to suggest readers should ignore these facets and focus only on the accuracy of the science. Still, I think the science angle shouldn't be ignored simply because a work has literary value - and especially when a book uses so much scientific terminology in a way that will leave many readers with the impression it is scientifically realistic.
A major part of the plot is based on the premise of some kind of quantum technology that allows connecting different areas of space-time by tunnels and other means. On the great scale, it's rather vague what and how this is done. And perhaps these large scale tamperings with space-time are just too far beyond my knowledge of physics to have an intelligent opinion how consistent with science it is.
However, on the smaller scale, "quantum teleportation" of people is common in the book and was less convincing to me. What is happening is not a stable wormhole large enough to walk through, nor probabilistic behavior sometimes resulting in a tiny minority of particles on one side of a barrier appearing on the other side of the barrier. We have teleportation of people - requiring no external device on either the sending or receiving end, and apparently requiring no more energy than a humanoid body possesses. A person "teleports himself", what does that mean in practice? If the person has a specialized "teleporter organ" in him that carries out the teleporting, how does that organ get teleported? If "quantum teleportation" means sending objects as individual quanta, at some point in sending the quanta making up the "teleporter organ", there will only be part of the organ left which will be unable to function. If this organ causes the person to teleport as one complete object, what is "quantum" about the process? (One could, in theory, solve this problem by having two teleporter organs, send one of them to location B and then have the organ at location B teleport the other organ over. But in Olympos, it isn't possible for a person at location B to teleport a person from location A to location B.)
Also, according to Olympos, a person doesn't have to know where in space-time they are teleporting to - only to be able to conceive of the place. For instance, there's a person (who has little knowledge of the physical sciences) teleport himself to a spaceship traveling from Mars to Earth. The ship has traveled a long distance since he last saw it and he has no way of knowing precisely where it is at this moment. But by thinking he wants to go to the ship, he appears safely inside the ship. This struck me as magic.
Perhaps of even more concern are the references to Setebos feeding on some residue of human suffering at places atrocities occurred centuries ago. This is not presented in the sense of a sadist who enjoys watching or causing suffering. We are told suffering leaves some attribute in those places. Such ideas play a part in some horror stories, but have little basis in science. Also, human emotions have biological foundations in our physiology - distinct to our evolution. Just as humans are unlikely to enjoy the taste, gain nourishment from and not be poisoned by plants and animals that evolved independently on other planets, it's unlikely an alien that fed on "emotional substance" would enjoy the taste, gain nourishment from and not be poisoned by human "emotional substance".
And I certainly react against the suggestion that authors or other artists cause their fictional creations to have a physical reality. I can't take seriously the idea that just because some imaginative person can conceive of Frosty The Snowman that in our universe (or in a newly formed universe that is like ours in every other way) a child-made snowman can walk, talk, sing and dance. If the thoughts of one person (using the energy available in one brain) can make such a large change to the laws of physics in our universe or create an entirely new universe with people and planets, then our understanding of physics is vastly mistaken. We can't be absolutely certain physicists aren't mistaken, but how can we be absolutely certain snowmen never sing and dance? I'm just not ready to consider Frosty The Snowman to be SF.