The Cost Profit report will give you the totals you are after.  The report can be found under Reports, Sales Analysis, Cost Profit Report. I created a sample report design called “Dollar Value by Book Class”.  Select the report and look at the design. In the report designer the Cost Profit field selector has some “begin” fields which represent the beginning value for the period.  The reports is coded to only show totals, so it will be short and not display all the product by product details.

The Period on which to report should be by month, so that the beginning values are for the first of the month. For the inventory at the end of August, you would select September.  The lower portion of the screen selects the products to be included on the report.  I saved a query called “DollarValue” as a sample. The sample selects all the “7” book classes in store1 that have a beginning inventory value.  The report, even though it will be short, uses a lot of memory as it analyzes and sums up each product in the selected range.  Because you have so many inventory items you will need to break the report up into segments.

Depending on your needs you may need to adjust the report and selection criteria.