Full disclosure: I don't really care that much about trains so I thought this museum would be a snooze-fest, but it was actually quite interesting.
The huge display of trains, many of which you can walk through, gives a nice hands-on lesson in the history of trains and their influence on Japan. There is some English signage, but if you have a smartphone you can download the English explanation for most of the displays using the barcodes on the corresponding signs. This was a nice feature, especially if you are interested in the details and intricacies of a particular train (or, for instance, if you have always wondered just how a locomotive works)
If you have already used Japan's railway system, then some displays, especially the newer train cars, will seem rather pointless to walk through. But the older models are rather fun to explore.
There is also a large model train set-up that is popular with the small kids, a room filled with scale models of trains, a collection of simulators (drive a train!) and a outdoor area with train rides, small "trains" you can actually "drive." This was very popular with the littler kids also.
Although I did not eat at the restaurant, it appeared to be fun! There was a wide selection of train-style box lunches. Unlike the ones you can get at a real train station, these appeared to be fresher and better quality. So, if you want to keep with the train theme, eat here.
Naturally I would recommend this place to anyone who is really into trains, but also to families with young children as there is plenty for them to explore and touch. Finally, if you are like me and not really excited by trains, it is worth a couple of hours to take a look and perhaps build an appreciation for the transportation method that makes a trip through Japan easy and fun