I think what the OP is really asking is - is it an extra venial sin to read the bible WHILE sinning venially.
Smoking isn't necessarily a sin if done in moderation, so if one is smoking in moderation, then there would be no extra sin by reading the bible doing so.
However, if one is addicted to the pleasure beyond reason (or harming health or giving scandal), I think there would be extra venial sin to be doing so while reading the bible, akin to the principle that if you venially sin on a Sunday or Holy Day of obligation, the sin is more offensive to God (though never turning a venial sin into a mortal sin).