Time Travelers Never Die

Time travel books all have to fight with the "believability" problem. If time travel works, why haven't we seen a bunch of them? The explanation this author uses is that time travelers can't "change" events. An attempt to go back and change a known past event will result in the death or displacement of the person attempting it.

However, this doesn't mean that time travelers can't have an impact on history - just that their impact has already been registered in history. (However, what happens if a time traveler decides not to perform an already past intervention? Or does it just require a Calvanistic predestination?)

Also, time travel seem to be limited. The father of the protagonist has discovered it. His research partner died in an attempted meddling, leaving only his son and friends with possession of the devices. Some asides seem to imply that the possibility of public time travel is acknowledged. However, it does not seem to have spread through society. (And the travelers don't seem to run in to others.)

Beyond the premise, the story is of two "historical voyeurs" - a version of Bill and Ted's Excellent Adventure played straight. This two guys love to go to historical events and hobknob with historical figures. This comes across as even less believable than the time travel. Would Ben Franklin even be able to understand their English, much less be taken aback by their dress and mannerisms? And the ancient Greeks and Renaissance Italians? Sure they have studied the classical languages and gone to costume shops, but would that really get them the full access they seek? And how many of these events really occurred as we "know them"? (To his credit, he does hint at a few things occurring on different days.)

On one spontaneous trip, he goes tens of thousands of years to the future and is enchanted to hear an orchestra playing. It seems humanity has survived the big scares of the modern days. (Though, I wonder what somebody from 30,000 years ago would think if they came to our day? Humanity as they know it may not be recognizable.)

One interesting side project they do perform is the restoration of lost Greek plays. They send them anonymously to a scholar, who disregards them, but then comes to believe they are authentic. Others, almost universally believe they are forgeries. However, when performed, they are positively received, and acknowledged as being either authentic, or the work of a great modern playwright. How would we accept new knowledge that is given to us?

The book has a few interesting points, but it is bogged down with excessive visits to historical events.