How lovely to walk along some of the streets in Prague, described (but not always named) in Kafka's writings. I felt that I already knew some of the streets in Prague from his descriptions.
The museum places a good emphasis on his writings, with photographs, historical and geographical contexts presented to help one get under the skin of Kafka's literature. It was helpful to see how he was shaped by his family and childhood, and this was well presented in the museum.
I spent an enjoyable morning in the museum and left feeling that I'd spent my time well, so around 3 hours would suffice for most visitors.
Quite a good museum shop, although sadly not all his publications were available as English translations.
If you haven't read any of Kafka's works, this museum will provide insight into his works and should spur you on to try some of his short stories or novels. If you've already read some of his work, this museum adds a further dimension to his work and to the man himself.
Enjoy!