Let me start off by saying I'm fairly new as well, but I won't let that stop me from putting my foot in my mouth:

Perhaps this behavior is dictated by my choices of data structures vecS?

This would be my guess as well. Did you try using a different structure to see if the behavior changes?

Is the Boost book is (substantially?) better than using the online docs, or is it just the same content on paper?

I found the BGL book to be helpful to a certain degree. The walkthroughs and examples seem easier to follow, and the index and table of contents are helpful to have at one's fingertips. Unfortunately, it is a bit old and so some important features are not covered in the book at all (property bundles, subgraphs). For those you have to rely on the online documentation. Nathan