I remember when my parents got Myst several years ago, or at least my mom did. She didn't want me to play it without her at first, so I just watched the making and I was so intrigued, even at only 6 years old, that I couldn't help but start a new game without her.
Over the next several months my parents and I worked at that game through, since we were new to the genre, and kept the original paperback journal full of our notes, sketches of maps, notes of where things were.. It was amazing. I don't think I've ever gotten so into a game until I got Riven.
Both games are truly a must-have and encourage critical thinking -- something we really lack in modern games. 5/5 from me!