Unbound is the second installment in the Songs of Chaos series, written by Michael R. Miller, being the direct sequel to Ascendant. And honestly, it feels like a step up at all levels, starting from passing from a single POV used in book 1, to making this second story one following multiple POVs, including the villains to being this a more complex story, expanding the world in the process.

Holt Cook and Ash saved the kingdom against all the odds, becoming outcasts in the process, and now are in a quest trying to unite the Elder Dragons against Sovereign and the scourge. His only option is to progress in their bond, while surviving the persecution of the riders and Soreveign's servants.
Talia and Pyra have returned to Feorlen, accepting Talia the role of rider queen, something unacceptable for the Order. Her councilors are not willing to hear her warnings about the danger Soreveign and the scourge are from the kingdom, and other countries are threatening to enter into war against them unless Talia navigates this complex situation with mastery.
Sovereign intends to discover new dragon powers, after what happened in the meeting with Holt and Ash, using his servant Osric as his tool, even against his will. More and more riders and servants are uniting his ranks.

But the half-dragon Rake seems to have the plan to stop Sovereign, needing to assemble a team to strike on the fortress, and at the same time, will act as a new mentor for Holt and Ash. They need to strengthen their bond, and Rake is prepared to do what will be necessary.

The addition of several POVs to this story helps create a more epic feeling while reading it, making the spectators more conscious about the real threat Sovereign is for our riders. At the same time, being able to know more about the villain and his plans works well as a way to give him more depth.
At the core, we are still reading a high fantasy story, with some progression elements, but I have to say they are well integrated into the plot, feeling natural to the world, becoming almost imperceptible once we are immersed.

Pacing is what I felt seemed a little bit slow, being probably the aspect I personally liked less about reading this book. While it picks up and becomes faster once we pass the first half, Miller takes his time to put all the details into the story.

Unbound is definitely a great sequel to Ascendant, improving many aspects of the first book, and becoming a great preparation for the third book, Defiant; personally, I can't wait to see the next battle against Sovereign. If you like high fantasy with dragon riders, and strong bonds with companions, I will definitely recommend you to give a try to Songs of Chaos.