Sandbox

Those two should really be on the same category (Books ?)

jbook
http://extensions.joomla.org/component/ ... Itemid,35/
(under directory)

Joomlib
http://extensions.joomla.org/component/ ... Itemid,35/
(under amazon)

We can also find a category for:
Bibliography (under Documentation)
http://extensions.joomla.org/component/ ... Itemid,35/

extensions listed:
Joomla BibTeX, Bibliography, Joomla BibTeX Searchbot, OwnBiblio

As they are not the same but related issues, maybe you can find a way to put it together:

Category: Library
Sub - Books
Sub - Bibliography

Maybe under Vertical markets?
Or simple create a new sub for books (for jbook and Joomlib) also under Documentation

BookLibrary - http://extensions.joomla.org/component/ ... Itemid,35/
Librarything Module - http://extensions.joomla.org/component/ ... Itemid,35/
Collection - http://extensions.joomla.org/component/ ... Itemid,35/

Maybe under Miscellaneous?
And don't call them Amazon!!!