systemd pid file issues

If I use this, the pid file isn't being written. Ruing the service as root works, but that is not desirable for obvious reasons. I have tried everything I can think of, even creating the pid file in the user's home instead of /var/run but even there the file is never created.

[Unit]
Description=Calibre Service
After=network.target

[Service]
Type=forking
User=calibre
Group=calibre
RuntimeDirectory=calibre
RuntimeDirectoryMode=777
PIDFile=/var/run/calibre/calibre-server.pid
ExecStart=/usr/bin/calibre-server
--daemonize
--max-cover=600x800
--max-opds-items=30
--max-opds-ungrouped-items=100
--useame=calibre
--port=8080
--url-prefix /books
--pidfile=/var/run/calibre/calibre-server.pid
--with-library=/pub/Books

[Install]
WantedBy=multi-user.target