Since its debut, the ebook has come with a fair amount of philosophical baggage. Is it even a book? Is it the death of the book?

Introduce the concepts of lending and retrieving the elusive ebook and you could devote an entire grad seminar to what it all means.

So while the number of people reading ebooks has leveled off a bit, the terms by which publishers sell them to lending libraries are still very much in flux.

These days, the question driving the debate is whether publishers should sell ebooks to libraries at a higher price for a perpetual license, or at a lower price for a license that needs to be renewed.

According to Andrew Albanese at Publishers Weekly, the recent trend has publishers switching over from permanent arrangements to more limited models:

After a period of relative calm, librarians have expressed concern over the last year that the major publishers are pulling back from the library e-book market. Last September, Penguin Random House also moved from perpetual access to a two-year metered model, with top prices said to be in the $55 range.

And most prominently, last July, Macmillan drew criticism for implementing a four-month embargo on library e-books for new frontlist titles from its Tor imprint, alleging that library e-book lending was having a negative effect on consumer e-book sales.

The Hachette Book Group is the latest firm to get on board, moving from  perpetual licensing to a two year renewal model and charging lower up-front prices.

Generally speaking, this makes things tougher on libraries, which now have more administrative processing to manage (re-upping their list every couple of years) and will ultimately have higher long term costs if they keep renewing their licenses on popular titles.

Macmillan’s four-month library ebook embargo still stands as the most extreme model for this changing relationship, but no matter what becomes the norm, it looks like our most beleaguered friends in the libraries will feel the change the most.