...need some help (a reference, or book, that will explain how to export data
from Access to Excel) to create a formatted report with sub-totals.

e.g. this is an employee timesheet application that will export data from an
Access query into what must eventually be a report with department and
employee groupings and sub-totals of hours, with drill down on the
sub-totals.

I know how to do the "TransferSpreadsheet" method to get the data into
Excel, but how do I get it into a usable form once it is in Excel.

My guess is it must go into a "data worksheet" which then loads into a
separate "report worksheet", with column headers, sub-totals, formatting
etc.

The "data worksheet" will be updated monthly and the number of rows will
vary each time the report is run.