Devil's Tower — Stephen Donald Huff

In the first days of the zombie apocalypse, a military physician and small team of survivors must gather their wits, their weapons and their available resources to make a last stand. When nowhere seems safe and no-one seems immune to the rapidly spreading disease, they must choose a destination that is both attainable and sufficiently remote to assure their long term safety. It's a sheer stone tower standing alone over a remote frontier, as iconic as it is forbidding. It is also the location of humanity's last stand. Can zombies climb?