I have couple of ideas, for your already excelent program to improve it even more.
1.An Icon and Button to add books from the Harddrive, like in AMM.
(actually I don't understand, why your two programs are not more alike in theire options, as it should be almost the same code for both, on the other hand in AMM the very important feature to have a relative path for the Collection is missing, or how do I change the path to lets say 500 movies, when changing to another harddrive?)
2.On the Book Card next to the Local Path and the URL field I would like a button to jump to the directory or to open the book's webpage in my browser.
3.Great would be the ability to have an edition tab (or something similar) on the book card, where I could manage different Versions of the same book, like audiobook, ebook, hardcover and paperback. If one has a book more then once and in different formats, there would only be one book card and database entry neccessary to manage the different versions. (of course with individual pathes and urls linked)
Or the option to link several book card, lets say different versions of a book or of a series, so only one entry is shown at first in the list, expanding to all the book cards on clicking to it, like a subdirectory. This way the book card could stay the same, but one could easyly tidy the list view from double entries.
4.Some name cleaning feature. An editable list of prefix words, which are not used while sorting the collection, like "the, le, la, der, die, das... .
5.Sorting by last or first name of the author, having 2 fields in the database and the collums in the list view. (Or always sorting by last name, but the choice of displaying by first name or lastname first) This should be done in the main view and not by using the directory menu. But that already leads to the next point.
6.Faster sorting access. An treeview like in "Movienizer" or even better in "extreme Movie Manager", where one can sort the collection much faster, then with your approach. (would be great for AMM as well)
7.Option to change fonts size in list view. To squeeze more information onto the screen.
8.Mass editing of several entries, for example choosing some Books in the list view and being able to change the genre or any other field for them all the same time.
9.Dropdown field for editing the books language, for faster editing, and last used entry as an suggestion or an autocomletion.
10. A Narrator field as standart, so it can be filled automaticly by the internet serach.
11.List all the files of an audiobook as one, while searching the harddrive. Read codec information, calculate duration, and files size.
Options for seraching the harddrive, take the last folders name of a tree as file title, treat files in a folder with the same name and numbers as one.
I hope some of it can make it into your next release (please soon
Especially the sorting features. Off all the book databases, I like yours best, but testing a lot of them lately I found the above items missing in your program.
And alltough AMM is quite good, I have to say I chose "extreme movie manager" instead of your AMM because of its better options an sorting abilities. (Hope you don't mind mentioning it, but have a look at it, there are some features AMB and AMM should have as well.)