Replaced the fiddly 5-tuples with a new Book convenience class, allowing to reference fields via names instead of meaningless little integers. This turned up one case where the wrong little integer was being used, in informative progress output.  Fixed that too.
Replaced the fiddly 5-tuples with a new Book convenience class, allowing
to reference fields via names instead of meaningless little integers.
This turned up one case where the wrong little integer was being used,
in informative progress output.  Fixed that too.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator