You probably need to contact your library - the library has to purchase the licenses for their ebooks so it might depend on the acquisitions budget.
I apologize if this questions has been asked already........
and I understand that some books never become library books.
How long does it take for a new book to become available for check out at the library?
I am watching for Brad Melter's The Inner Circle. I read another of Brad's books checked out through the library. The audio copy became available almost immediately, but I'm not a listenter, strictly a reader
Typically if I am looking for a book, I check Overdrive first to make sure it is available to the library.
Like Melissa says, contact your library. My library's website has a link to request a book be added to the print library or to the digital library. I rarely request an addition, but when I have they are pretty quick to add the book.