This is a maintenance release. It doesn't add any new story content to the game.
Improved compatibility with the Steam Deck was the initial focus, followed by miscellaneous additions and improvements in no particular order.

Updates to the game

• fixes an expression which wouldn't load, causing the character to sometimes have a blank face
  
  
• updated game engine from Renpy 7.0.0 to 7.4.11
  
  
• updated several explanations in the knowledge base to make them more concise and hopefully easier to understand
  
  
• reworked screens to remove the need for scrolling (which complicated keyboard/controller navigation)
  
  
• added info button to the quick menu below the textbox, so it's easier to expand the infobox explanation when using a keyboard/controller
  
  
• disabled keyboard/controller navigation to infobox. The infobox could previously be focused and expanded by a keyboard/controller, but there was no visual indication, and it could be tricky to navigate between the quick menu, the textbox, and the infobox
  
  
• improved keyboard/controller navigation on credits screen
  
  
• added version number to main menu
  
  
• made music transitions smoother
  
  
• added setting to skip unread text
  
  
• added setting to save game on quit and automatically load the last save when starting the game. This is enabled by default. If you have an existing save from prior to this update, it won't automatically load the first time. But if you load the existing file and then save, it will automatically load from that point on.
  

Steam-specific changes

• the game is now in separate depots for Windows, Mac and Linux, which brings the download and install size down
  
  
• added steam capsule image for the new "vertical capsule" type, redid the "hero" image, and replaced some of the other images with higher resolution versions
  
  
• implemented cloud saves. Kind of pointless for a game of this length, but why not?
  

If you're unable to start the game after updating, please verify the local files.
You can do this by right clicking on Humanity Must Perish in your Steam library and selecting Properties.
Then go to the Local Files tab and click on Verify Integrity Of Game Files.

Steam handles conflicts with Cloud Saves pretty well nowadays.
Nonetheless, if anything does happen to your saves, you can find local backups of the saves on your PC in the following places:
Windows: %APPDATA%/RenPy/HumanityMustPerish-1486410470
MacOS: ~/Library/RenPy/HumanityMustPerish-1486410470
Linux: ~/.renpy/HumanityMustPerish-1486410470
You can copy these files, then right click on Humanity Must Perish in your Steam library and go to Manage -> Browse Local Files
Then go into game/saves, and paste the files you want to restore.

If you encounter any other problems, please report them on this thread.
You can also switch to the oldstable beta for the time being, though saves from the new build won't work on the oldstable build.