Bukkit

3.1.3

Java 1.6 compatible (for real this time)

Full changelog here

Copying multiple books at once (/book copy <quantity>) is horribly inefficient and will cause lag for higher quantities. By default the maximum copies per operation is set to 10. A fix will be available in a later version.

If the URL used importing a book checks out but takes too long to respond, an empty temp file can be created and never deleted. To fix this, reload the plugin.

Due to encoding differences, importing from sites that are not plaintext will cause issues for any special characters. Use a site that supports a plaintext view.
Bukkit pastes do support this, just add .txt at the end of the url, e.g. http://dev.bukkit.org/paste/gy7ekjupawivnbxq.txt.
A basic rule of thumb: If right clicking -> view page source doesn't look pretty much like your book, it might not work right.