As someone who also tried to hold code reading groups I agree 100% with the conclusion.
The first code reading session I held, I chose underscore.js and it was a successful code reading session, because -- unlike most libraries and programs -- a functional utility library was a nice linear read with mostly self-contained functions. However, when we got to more complex programs and libraries with more code to handle accidental complexity (e.g. handle browser and DOM inconsistencies, or UNIX fragmentation etc) it was considerably harder to read and the presenter found themselves jumping between different code paths and functions like they were debugging the program.
The first code reading session I held, I chose underscore.js and it was a successful code reading session, because -- unlike most libraries and programs -- a functional utility library was a nice linear read with mostly self-contained functions. However, when we got to more complex programs and libraries with more code to handle accidental complexity (e.g. handle browser and DOM inconsistencies, or UNIX fragmentation etc) it was considerably harder to read and the presenter found themselves jumping between different code paths and functions like they were debugging the program.