The Swarm: The Second Formic War
by Orson Scott Card and Aaron Johnston, 2016

Follows the protagonists from the First Formic War on their journey to prepare for the second alien invasion, some small number of years later. Time is a difficult concept in these books, as disaster always is made to feel imminent, but travel across the solar system takes months or years. First book in (presumably) a trilogy of books related to the Second Formic War.