You have PHP configured to use CGI. From your phpinfo: "Server API CGI/FastCGI". Also note that there is no Apache configuration information in your phpinfo output.
Whatever you are using for rewriting and dispatching is not recognizing php files in the middle of the path, which is what I said in my original answer to you. The message "No input file specified" is not generated by my server.
FWIW: I think that your library should not be kept in webspace (files visible by the web server). This is an invitation for piracy, because people can go directly to the books.
The reason that the title is provided as extended path is to give browsers a file name. Some browsers ignore the name in the content-disposition header.