Direct integration to Outlook Calendar is coming in late 2019. In the meantime, this workaround allows you to sync your appointments to Outlook as well as have Outlook Data synch with your automation account - to avoid double bookings.
In other words, this is a 2-way integration.
The tool you need to download is here: https://github.com/phw198/OutlookGoogleCalendarSync/releases/tag/v2.8.0-beta
Don't have a Gmail account? Set one up here: https://www.google.com/gmail/