My boyfriend and I are huge fans of WW1 and 2 history, so we were excited to visit. I found the Holocaust displays to be incredibly moving and my boyfriend enjoyed the section dedicated to planes. This is incredibly well done in terms of the quality of the exhibits and displays, but there isn't a lot. We got through the museum in a little over an hour and felt it was plenty of time.
Please note that as I mentioned above, the topics are very sensitive, so you may not want to bring children or those triggered by genocide.
The only reason I don't give this museum five stars is because of the Cafe - they really need more options in general, but especially allergy friendly options. I would recommend this museum to first time visitors to London.