Travelers - Unseen Things, #17

It was the year 2231 when they started coming through the portals. The echnids came looking for something specific, but that didn't stop them from wiping out eighty percent of the Earth's population, so they could also steal whatever other resources they found useful. Humanity may have been wiped out completely if not for what became known as the Day of Death, where all the echnids on Earth suddenly and inexplicably turned inside out.
Some people became victims in this post-apocalyptic world, while others, like Jake and Lana, found the strength within themselves to not only survive, but to thrive in this new world by taking on less than moral jobs in exchange for food, and all the other things they needed to make it from day to day. That all came to an end however when they reached the town of Cottonwood. The town was about the most normal and functioning place they'd run into in all their years of travels, and with life on the road weighing down on them so heavily, they decided that this was where they were going to settle down.
Unfortunately, as the new sheriff and deputy of the town, they have to deal with a variety of issues in order to protect the people of Cottonwood, including random echnid incursions, roving bands of a biker gang known as Skinks, a drifter who lives to prey on the weak, and a very angry pregnant girl from a nearby town who has a bounty out on Jake's head. Making things even more difficult, when a random guy passes through town and tells Greg about some doors he saw standing amidst the rubble of some bombed out buildings up along the coast of Washington, his first thought is that they're most likely the remains of some sort of an underground military facility.
He becomes so obsessed with this thought, and what it could potentially mean for the town if they were to go up there and actually find something, that he attempts to enlist Jake and Lana's help to make the trek up there with him. It would be a dangerous journey, but when four random strangers suddenly hit town, they might just have some information for them that'll save them from making a useless trip.
Travelers is book 17 of the Unseen Things series.