There have been some good suggestions about sorting the shelves and so forth, which will work great with physical books. But I have been looking for a solution for a growing ebook collection that I have. Sorting these is difficult enough, but having a "card catalog" type of database precents a different set of challenges. For instance, many of the ebooks, (pdf files) I have are not commercially available texts, and thus do not have an ISBN. And also, since their is not a barcode, barcode scanners would be useless.