Hi,
My guess, and it is only that, is what they mean is not that what you've given them is insufficient for them to visualise the world, but that they like it and want more. Can't think of the book at the moment, but there was one set in Ancient Greece which I enjoyed particularly for the side pieces. Every so often the author would go into small stories not related to the plot, such as a temple where an ancient prohecy was given which was of course misinterpreted with disasterous results. I mean the book was good but they just added colour.
Cheers, Greg.