I read this book aloud to my two sons, age 8 and 12. We liked it, but the first three chapters had too much background information on mining and history. We liked "Young Indiana Jones and the Circle of Death" much better. Young Indiana Jones and the Circle of Death (Young Indiana Jones, Volume 3)
Here's the blurb from the back of Ghostly Riders: "A holiday in Wales... in the shadow of terror!"
"The Wales that Indy visits is coal country. But long ago King Arthur and his warriors roamed there. So it's a great place to explore. And sure enough, Indy finds an ancient treasure!"
"But he finds danger as well... a ruthless plot to put a coal mine out of business! When Indy discovers who's behind it, HE could be put out of business too."
"Before Indy knows it, he's running for his life... and straight into more trouble -- a band of ghostly riders!"