Back in the 80s I borrowed a book series from a friend and never got to finish it. I've half looked around over the years and can't find anything that sounds even close to what I remember.
It started with a man in college, one day a strange device appears in his room and he finds himself trapped, eventually gets bored and starts messing with the device and ends up in the future. As time is moving forward he sees what looks like a war (everything is destroyed in a flash) and he sees the forest grow, get cut back and cottages taking their place, a few times.
I can't remember if he traveled hundreds or thousands of years, but it was referred to as the fourth or sixth era of man.
Telepaths are a small but growing minority who can be blocked by a wire mesh worn on your head, at some point in the past there was a war between the telepaths and 'normal" humans with the normal humans barely winning.
All readily available deposits of iron and other minerals have been depleted and with fossil fuels all but gone, mining has ground to a halt. The main character makes his fortune planting "iron berries" where the old cities of the 20th century used to be. These were plants specifically bred to extract iron and concentrate it as a small nugget in the middle of its fruit (hence its name) I think they also developed plants to extract gold and other minerals but don't quote me on that part.
He can use the device to do some short hops through time, but something happened right before the current era (the one in the future) that prevents him from going back to his own era.