It is basically Steam trying to get you to play your older games. Dewey, a little 8-bit robot guides you through your library suggesting what games to play next. Each level of your house have different themes. Like co-op games, new game, or really olde games. There are badges to collect, so the completionists among you might be interested.
I actually played all the games they wanted - for the few I didnt have installed I chose the option that was the smallest download - literally just start the game for 5 mins and leave. Press F5 and you will get the next one