If you have an Office 365 subscription, your Office will be upgraded to the latest version automatically without doing anything. How to download Office 2019 from Microsoft homepage And I think Office 2016 is still a good choice for casual users at the moment.
Honestly, I hate what Microsoft have done to force users to use Windows 10. So if you are using Windows 8.1 or older versions, you will not be able to install it. However, I regret to inform that according to the disclosures, Microsoft Office 2019 only works on Windows 10. It is stable one, this means you can download and use it right now without worrying about fatal errors which you have gotten in beta versions before.
After a series of preview versions, Microsoft finally came out with an official version of Office 2019.
