Valve recently updated its Steam service with a much wanted feature where games can be played whilst a download is taking place. Previously, the download would stop when a game was launched, and required, Alt Tabbing to resume the download which was a bit fiddly.
Here’s how to enable background downloads on Steam:
Go to Library
Right click the game you wish to play
Tick the box which reads: Allow Steam to download other updates while this game is running.
This will have to be done for each game you intend to play, which is a bit odd there’s no global setting here. Either way, it’s a welcome addition and works wonders.