[chaley]

You can do what I said I do in post #5 of that thread:
- use "monit" to monitor the timestamp of metadata.db. It restarts calibre if the timestamp changes
- use monit to ensure that the server is actually running
- have the calibre start/stop script copy the database to /tmp
- set the environment variable CALIBRE_OVERRIDE_DATABASE_PATH to tell calibre where the db is located

I don't use a start/stop script in /etc/init.d. I let monit take care of it.

I run debian wheezy. The relevant monit sections are

check process calibre-server with pidfile /var/run/calibre-server.pid
  start program = "/root/mon/calibre-server.sh start"
  stop program  = "/root/mon/calibre-server.sh stop"
  alert YOUR_EMAIL_ADDRESS_HERE only on { timeout, nonexist }

check file metadata.db with path /home/dropbox/Dropbox/Charles/Library/metadata.db
  if changed timestamp
     then exec "/root/mon/calibre-server.sh restart"

The start/stop script that monit uses (/root/mon/calibre-server.sh) follows. I blatantly stole it from an init.d script.

Spoiler:

#! /bin/sh
# Author: YOUR NAME HERE
#
# Please remove the "Author" lines above and replace them
# with your own name if you copy and modify this script.
# Do NOT "set -e"
# PATH should only include /usr/* if it runs after the mountnfs.sh script
PATH=/sbin:/usr/sbin:/bin:/usr/bin
DESC="Calibre Content Server"
CONTENT=PATH TO YOUR LIBRARY (FOLDER WITH BOOKS) HERE
NAME=calibre-server
DAEMON=/usr/bin/$NAME
PIDFILE=/var/run/$NAME.pid
DAEMON_ARGS="--with-library $CONTENT --pidfile=$PIDFILE --daemonize -p YOUR_PORT_HERE "
SCRIPTNAME=/etc/init.d/$NAME
# Exit if the package is not installed
[ -x "$DAEMON" ] || exit 0
# Read configuration variable file if it is present
[ -r /etc/default/$NAME ] && . /etc/default/$NAME
# Load the VERBOSE setting and other rcS variables
. /lib/init/vars.sh
# Define LSB log_* functions.
# Depend on lsb-base (>= 3.0-6) to ensure that this file is present.
. /lib/lsb/init-functions

export CALIBRE_OVERRIDE_DATABASE_PATH=/tmp/metadata.db
#
# Function that starts the daemon/service
#
do_start()
{
        # Return
        #   0 if daemon has been started
        #   1 if daemon was already running
        #   2 if daemon could not be started
        cp $CONTENT/metadata.db $CALIBRE_OVERRIDE_DATABASE_PATH
        start-stop-daemon --start --quiet --pidfile $PIDFILE --exec $DAEMON --test > /dev/null || return 1
        start-stop-daemon --start --quiet --pidfile $PIDFILE --exec $DAEMON -- $DAEMON_ARGS || return 2
}
#
# Function that stops the daemon/service
#
do_stop()
{
        # Return
        #   0 if daemon has been stopped
        #   1 if daemon was already stopped
        #   2 if daemon could not be stopped
        #   other if a failure occurred
 
        start-stop-daemon --stop --quiet --retry=TERM/30/KILL/5 --pidfile $PIDFILE 
        RETVAL="$?"
        [ "$RETVAL" = 2 ] && return 2
        # Wait for children to finish too if this is a daemon that forks
        # and if the daemon is only ever run from this initscript.
        # If the above conditions are not satisfied then add some other code
        # that waits for the process to drop all resources that could be
        # needed by services started subsequently.  A last resort is to
        # sleep for some time.
        start-stop-daemon --stop --quiet --oknodo --retry=0/30/KILL/5 --exec $DAEMON
        [ "$?" = 2 ] && return 2
        # Many daemons don't delete their pidfiles when they exit.
        rm -f $PIDFILE
        return "$RETVAL"
}
#
# Function that sends a SIGHUP to the daemon/service
#
case "$1" in
  start)
        [ "$VERBOSE" != no ] && log_daemon_msg "Starting $DESC" "$NAME"
        do_start
        case "$?" in
                0|1) [ "$VERBOSE" != no ] && log_end_msg 0 ;;
                2) [ "$VERBOSE" != no ] && log_end_msg 1 ;;
        esac
        ;;
  stop)
        [ "$VERBOSE" != no ] && log_daemon_msg "Stopping $DESC" "$NAME"
        do_stop
        case "$?" in
                0|1) [ "$VERBOSE" != no ] && log_end_msg 0 ;;
                2) [ "$VERBOSE" != no ] && log_end_msg 1 ;;
        esac
        ;;
  status)
       status_of_proc "$DAEMON" "$NAME" && exit 0 || exit $?
       ;;
  restart)
        #
        # If the "reload" option is implemented then remove the
        # 'force-reload' alias
        #
        log_daemon_msg "Restarting $DESC" "$NAME"
        do_stop
        case "$?" in
          0|1)
                do_start
                case "$?" in
                        0) log_end_msg 0 ;;
                        1) log_end_msg 1 ;; # Old process is still running
                        *) log_end_msg 1 ;; # Failed to start
                esac
                ;;
          *)
                # Failed to stop
                log_end_msg 1
                ;;
        esac
        ;;
  *)
        #echo "Usage: $SCRIPTNAME {start|stop|restart|reload|force-reload}" >&2
        echo "Usage: $SCRIPTNAME {start|stop|status|restart}" >&2
        exit 3
        ;;
esac

The rest is up to you.