Herbert Hoover took over after winning an election after Coolidge decided not to re-run for office.
He was a bit of a reformer, going after tax cheats and gangsters. It was under his term that Al Capone was targeted for his crimes.
Hoover was rather mum on the issues of civil rights. Ironically he had the first Vice President (Charles Curtis) with a majority of Native American ancestry.
The biggest thing about his presidency was easily the Great Depression. He had some good ideas, but I feel like they were rather half-assed attempts that were very flawed or just a little too late for it matter. People needed governmental assistance when the private business world crashed and burned, and obviously got ignored.
Hoover might not have been one of the worst presidents ever, but he's a bit of a joke. I think he had some good intentions, but he wasn't very good at pushing an agenda or being remotely decisive.