It's not just you, Steam is currently down for maintenance in seemingly all areas with unofficial reporting site steamstat.us indicating that 100% of the service is down.
So the good news is that you aren't alone in your access to Steam not working and given that it is Tuesday, we know that this is just the routine maintenance that Valve inexplicably doesn't offer specifics on.
When will Steam be working again?
While again Valve isn't helpful in this regard, we do know from past experience that it typically takes about half an hour for it to come back online. That would suggest that we can expect it to come online again at around 7:00 PM ET.
So either turn to one of your other favorite gaming platforms or just have a quick snack as you shouldn't need to wait too long for Steam to be up and running again.