A definite must have for gaming groups!
I have ran tabletop roleplaying games for decades (since approximately 1984). Everything from Dungeons and Dragons Basic set (in the box), Battletech, Shadowrun, White Wolf, and a dozen other systems (that maybe I will do reviews on someday).
I have recently reread the book this year for a new campaign I am running and I am reminded why I use it. Because you can recreate any world you want with these rules. The fact that you can modify the setting, genre, realism level of the game, makes it the best choice.
Pros: A variety of settings are provided in supplements and sourcebooks with constant updating of different worlds and even additional advanced rules, equipment and ideas. You want gritty realism, or cinematic campaign you have it. Do you want a combination of Cthulhu and Shadowrun? What about Fantasy and Werewolf? You can do it all.
Cons: In all fairness this is not an easy system to learn. It is prohibitively complicated for new players or GMs, and even those with lots of experience will still struggle a bit. The rules can bog down the game so you will have to learn to cut the things you don’t want to deal with. This is why I can’t give it a 5 star and only a 4 star.
Overall it is my favorite systems and with patience you can convert any other game system into GURPS (my most recent one was converting Mechwarrior/Battletech into GURPS and it was better than the original system because of more RP character options).