I recall buying Portal by Activision for Amiga at a local shop without having read any reviews before; as a huge sci fi movie/games fan I thought it was a sort of adventure like game but got hugely disappointed after discovering it was "just" a novel. My less than adequate English knowledge back then also prevented me from appreciating it for what it was, so I tossed it in a drawer before finishing it until the day I sold my Amigas.

It's a different game, same name. The Activision game is a hybrid text adventure following after Infocom Zork-likes. This one is the puzzler by Valve.

actually Activision's portal was an amazing experience because yes it's a novel but you're the main character. You're an astronaut that arrived on Earth 100 years after you left and no one is on Earth. You find a single working computer terminal. The "game" is your terminal for you to use to figure out what happened. it's pre websites so looks like 80s ideas of info but I loved it

Sorry, I didn't make that clear: Activision got to the name first. I enjoy both Portals. :)