cost of goods sold is supposed to represent your cost of the books sold.
"I keep track of what it costs to produce each book (design, printing, etc), then I multiply that by the number of books I sell" I'm assuming what you're saying is that if you produce some books for $4 and some for $12 you compute the cost of sales by multiplying the number of $4 books sold by $4 and the number of $12 books sold by $12.
so Beginning inventory
+ cost of production of books for the year
- cost of books sold during the year
= ending inventory
so if beginning inventory is $38,635 and current year production costs were $7,495 your inventory before any sales would be $46,130. if you properly valued the ending inventory at $31,615 that means you disposed of inventory having a cost of $14,515 which is the cost of goods sold.
