Cool visualization, but the model needs work. The closest book to "Harry Potter and The Chamber of Secrets" is "The Victorian Lady's Guide to Sex, Marriage, and Manners".
There's probably a graph theory phenomena that describes what I'm thinking.
Basically just prune the top and bottom %1 of weighted edges to get an appropriate average. Would be my guess for a fix.
Within our data books like lord of the rings and harry potter are nearly impossible to map for "books like" because they are connected to so many other things. I am working now to fine tune our model, but it has been an interesting challenge.