The Lighthouse Between Worlds, by Melanie Crowder.
Griffin and his father tend to their lighthouse on the coast of Oregon each day, carrying out the same diligent routine. It's so isolated, there are no visitors, but that's how they like it. Until one day, when a group of oddly-dressed strangers appears. Griffin learns that the lighthouse holds many secrets: a portal to multiple dimensions, the hostile entities that lurk beyond, and a Society of Lighthouse Keepers tasked to keep these enemies at bay. Then his father disappears into the portal, and no-one will give Griffin the answers he wants. So, he'll have to find his own answers, armed with a book of cryptic notes and drawings his parents left behind. Griffin is determined to find his father at all costs, but the realm beyond the portal is far more dangerous than he could have imagined...