Print on demand is a way of printing items for a fixed cost per copy, regardless of the size of the order. While the unit price of each book is higher than with offset printing, the average cost is lower for very small print runs, because setup costs are much lower.
Print on demand has other benefits besides lower costs for small runs:
Book Services usually prints its books using Lightning Source or Create Space. Distribution is typically done in the U.S. through Ingram, Amazon.com, Baker & Taylor, and Barnes & Noble, among others. International distribution is also available.