Who is buying my Green Technology Strategies book?

The notes for my course "ICT Sustainability" are available as a paperback book from Lulu, a print on demand service: "ICT Sustainability: Assessment and Strategies for a Low Carbon Future". This has not exactly been a best seller, with a sale every day or two. What is curious is that the previous edition "Green Technology Strategies", is selling much better. In February, 46 copies were sold. Most of this was one bulk sale to Ingram and most of the other recent sales have been through Ingram. Who are buy the book? Why don't they buy the new edition? Should I withdraw the old edition?