Hollow World - Michael J. Sullivan

Ellis Rogers is an ordinary man who is about to embark on an extraordinary journey. All his life he has played it safe and done the right thing, but when faced with a terminal illness, he’s willing to take an insane gamble. He’s built a time machine in his garage, and if it works, he’ll face a world that challenges his understanding of what it means to be human, what it takes to love, and the cost of paradise. He could find more than a cure for his illness; he might find what everyone has been searching for since time began…but only if he can survive Hollow World.