Maybe it's me, but I like those kinds of "extraneous" chapters, like the whale anatomy chapters in Moby Dick or the 8 million "Still Knitting" chapters in A Tale of Two Cities.

For the record, I did read an abridged version of Les Mis and felt like a lot was missing/inaccurate, which I found extremely frustrating. Reading the full-length version was much more comfortable. *shrugs*