LF Games like Myst or Riven

[Nasdaq]

Hi,

my mom is playing Myst and Riven for such a long time and now she's a little bit bored of it.
There are no other games she like to play and now I want to ask you, if you know any games like Myst or Riven.

The Click-Adventure-Puzzle style but for adults

I don't want to recommend her to play the Runaway trilogy because it's too childish imho.
(Don't know if Runaway is known outside Europe?!)

Thanks for any suggestions

[Pshaw]

Grim Fandango, if you can find it someplace.