Halo Glasslands follows several different groups or characters. You follow Dr. Halsey, the remainder of the Spartan-IIIs and Spartan-IIs from Onyx, and SCPO Franklin Mendez. Then there is Kilo-Five, which is made up of a S-II "dropout" Captain Serin Osman, Spartan-II Naomi-010, ODSTs Vasily Beloi, Malcom Geffen, and Lian Devereaux, and a "smart" AI Black Box, AKA BB. And Finally, there is Avu Med 'Telcam, and Jul 'Mdama.
Halsey, Mendez, and the Spartans are still in the Forerunner Shield World, and are looking for food, shelter, etc. While investigating something she saw move, Lucy-B091 wanders off from the team, and accidentally walks through a wall. You may remember from the beginning of Ghosts of Onyx, that Lucy was traumatized during a mission (OPERATION: TORPEDO) where her entire team, except her and and Tom-B292 died. After that, she never talked again. So Lucy couldn't radio Halsey and the rest of the Spartans for assistance. She explores this new area for a while, and comes across several Forerunner, not Covenant, Huragok (Engineers). She begins communicating with the Huragok via a large touchscreen. Eventually, the Huragok help her out of the "room" and meet up with the rest of her team. Halsey has a field-day communicating and asking the Huragok questions. They later convince the Huragok to let them send a distress signal out. After they get a reply from Parangosky, the Huragok are convinced that it is safe to bring the Shield world back to normal space.
Meanwhile, Kilo-Five is on a mission to spark an insurrection within Sanghelios. Captain Osman, under the orders of Margaret Parangosky, is supplying Avu Med 'Telcam with weapons. 'Telcam wishes to remove Arbiter Thel 'Vadam from power, and (unbeknownst to the UNSC) defeat the humans before they can regain power. But don't think too low about him, because that is exactly what Parangosky is trying to do to the Sangheili. Later in the story, the UNSC picks up readings coming from where Onyx used to be. Kilo-Five is sent to investigate. Eventually, the Shield World is brought back to normal space. In normal space, it grew to the size of an entire solar system. Not just empty space though, land, and lots of it. They find Forerunner ships capable of pin-point slipspace accuracy, and even though the Huragok wont allow themselves, or the ships to be removed from the Shield world, they create several new Huragok special for the humans. It is later requested that the shield world be named Trevelyan, after Kurt-051, who sacrificed his life for Halsey and the S-IIs and S-IIIs.
Jul 'Mdama is a former Covenant Shipmaster, who thinks the humans should be finished off. He joins forces with Avu Med 'Telcam, who is part of Servants of Abiding Truth. They try to assassinate Arbiter Thel 'Vadam. Towards the end of the story, 'Telcam sends a note to Prof. Phillips, telling him to meet him at the SoAT's "headquarters". Then, after talking with Telcam a few minutes, there was an explosion. And all Osman could hear on Phillip's microphone was Telcam, shouting, "It's not us. It's not us! What in the name of the gods is happening?" I'm not sure exactly what that means, but it could either be residual Covenant forces, or humans. Or could it be Forerunners? I wouldn't bet on it, but there's always the possibility. We'll just have to wait for the sequel.
All in all, Glasslands would have to go in my Top 3 favorite Halo novels. I really enjoyed the exploration of Forerunner technology, as well as going deeper into Sanghelios than ever before. I'm not sure I like the fact that humanity's "alliance" with the Sangheili might not last. I kind of liked the idea of rebuilding society side by side. And in Halo 2 and 3, I felt 10 times more awesome fighting alongside Spec-Ops Sangheili. It wasn't 100% what I expected, but it is definitely a must-read for any Halo fan.