Blightfall: Skyward Legacy 1 by Brandon Sanderson

After decades of war against alien oppressors, the humans of the Defiant Defense Force are finally free. Yet for Arturo Mendez, leader of Skyward Flight, freedom isn't what he thought it would be.

His first postwar assignment seems simple: The DDF has found evidence of other settlements of humans who were isolated during their long war against the aliens, and Arturo and his flight of pilots are to escort a team of diplomats as they attempt to make contact. It's an easy mission-get in, guard the diplomats, and get out.

But no element of this mission turns out to be simple. Blightfall is inhospitable, surrounded by mysterious debris and covered in giant, invasive forests that have swallowed most of the planet. Upon arrival, Arturo's team is attacked, and it quickly becomes clear that this human settlement isn't what it appears to be.

Now trapped in an unfamiliar world and unsure who to trust, Arturo and his team must find allies and uncover long-buried secrets if they hope to escape and return home.