We went here when we were on the Washington DC trip. The museum was very serious and had all sorts of things. It had newspaper articles involving the Holocaust. It had movies, and signs to read. It even had a boxcar from the Holocaust, that you had to walk through to get to the next part of the museum.
Here is the link to the website.
The website has information about the Holocaust and the museum. It shows the museum exhibitions and talks about the Holocaust.