J L.
Google
A great place for a quiet day trip. There's a place for reading thousands of picture books in multiple languages, which is where families with young children (and solo adults) could spend hours reading. There was an exhibit on the history of picture books. All the explanations were in Japanese, but many of the texts themselves were in English. In addition, exhibits on Beatrix Potter and a special exhibit on American picture books meant that we spent a fair amount of time wandering around.
Finally, the picture book shop was very fun. The books were from all around the world, and in both English and Japanese.