I had to try the tren turistico out of curiosity.
It is a road train with carriages which does an interesting route of Granada.
There are free headphones with commentary in several languages.
It is a hop on hop off service which means after paying for the ticket you can get on and off as many times as you like.
My opinion:
It is very touristy and it makes you feel like an obvious tourist.
It is a little bit expensive and it would be cheaper to get in a taxi and do the same route or just get on one of the normal minibuses.
However it is a pleasant way to spend some time in Granada and could be fun for a lot of people.
Click here for more information.
https://granadainfo.com/alhambra/tren.htm