This is an interesting time-travel tale that begins over a thousand years ago in North America and ends up in a parallel Universe where World War II ended very differently.
The crew of the time ship Oberon is investigating the destruction of the Hindenberg. Two of the agents from the future are disguised as passengers. But the disaster never happens--and because of this an alternate time-line is created. And the repercussions of this time-line causes the end of the world.
The most interesting part of this the character Murphy, who is a physicist in present day 1998 with aspirations of becoming a science fiction author. He writes that UFO's are most likely time machines--which is right! When the Hindenberg incident happens, the time travelers go back to Murphy's time and he's a bit different.
This isn't the best time-travel book I've read nor the worst, but falls squarely in between.