Book about a colony ship failing and the colonists returning to an empty Earth

Question

I'm looking for a book I read once but I don't remember the title. The gist of the plot is this:

A spaceship carrying colonists leaves Earth traveling perpendicular to the galactic plane. The ship is fueled by a large tank of antimatter. As their journey proceeds, strange, unexplained things start happening on-board. Then all their antimatter fuel disappears. They decide to abandon ship and return to Earth.

When they get back, all the people are gone. As they search the spaceport for people, one of the colonists explodes. Then another. Eventually they run into a person who is actually God. He says that the galaxy and humans were an experiment and since the people decided to leave the galaxy, the experiment was over. God took all the people and stacked them in Carlsbad caverns. The colonists ask God to restore the experiment and he does, saying that He'll leave it alone for a while, implying that He'll be back to end it again maybe in a day, a year, or a thousand years.

Anyone know this book?

Answer 1

This would appear to be Forever Free by Joe Haldeman.

Surrounded by a society that is too autocratic and intrusive, living a dull existence which cannot compare to the certainties of combat and feeling increasingly alienated, the veterans plan an escape to the future by means of space travel and relativity. But when their ship starts to fail, their journey becomes a search for the Unknown, the elusive entity responsible.

On returning they find Earth deserted and everything gets more strange from there.