The original Gabriel Knight trilogy, a pair of Caesar city-builders, and more Sierra-published titles have gone up for sale on Steam today. If you like fearsomely difficult adventure games, there’s plenty to choose from.
Perhaps you’d like the Police Quest Collection, in which the early games were so admirably dedicated to correct police procedure that you’d see a ‘Game Over’ screen for running red lights or forgetting to check everything in your car. Gabriel Knight is a little bit kinder in general, but is also the source of the infamous cat moustache puzzle. The first game’s also really good (I can’t vouch for the rest because I haven’t played them, they may also be really good!)