This one is really hard to review.

On one side, the first parts of the adventure are quite nice and Mokmurian's story is really great and deep, but I can't like the way the adventure is handled in the last 2 parts (under Jorgenfist).
A "one room = a strange creature different from all the others = a foe to beat without speaking" structure is called in France "Portes Monstres Trésors" (for Doors Monsters Treasures, I don't know if there is an equivalent term in english). It is for me the more simple but also the more stupid (no offence there to Wolfgang Baur) way to design an underground place in RPGs. I have a hard time to believe in this dungeon ecology (with giants next to dragons next to lamia next to trolls next to a kobold hero, etc.). Indeed, the foes are varied and interesting in term of game design, but that's all : it's all about fights, there is no really place for roleplaying in these last two parts, except with the female elder stone giant. Without her and the mechanical librarian, this adventure would feel blank and repetitive.
--> Back story and main foe background : 4/5
--> First parts : 3/5
--> Last two parts (the main parts) : 2/5

On the other side, the articles on stone giants and dragons are really great, especially the dragons' mythology one. --> 5/5

So I will give this book a harsh 3/5 rating.

Apesar de ser uma excelente aventura de dungeon, eu achei um pouco inferior as outras. Talvez seja apenas meu gosto pessoal, mas eu entendo a necessidade de ter aventuras assim. De qualquer forma, achei muito divertida de jogar e com certeza vai satisfazer os fãs de aventuras mais voltadas para exploração de masmorras e combate. Os artigos são muitos mais uteis para quem não joga em Golarion, mesmo que seja apenas com ideias (e o material deles até hoje não foi repetido, sendo a única fonte de histórico pesado sobre os gigantes e dragões). Adicionando aos monstros (estes foram recentemente atualizados para o Pathfinder RPG no Bestiary 2) tornam esse volume bastante recomendado para se ter na estante.

The Most excellent Rise of the Runelords Adventure Path continues with our heroes facing an army of Stone Giants on their turf! The real danger is the library! Check out my full review: Fortress of the Stone Giants

Disclaimers:
Review may contain spoilers
My Experience with it:
DM for one 3.5 Group and one PFRPG Group (as is, no conversion)
Overview (no spoilers):
Old school feel, a lot of hack and slash, memorable Boss-fight
Changes (with spoilers):
I replaced all the new monsters (except the black monk) with old school monsters to enhance the old school feel, I printed the northern half of Sandpoint to scale, emptied my living room and covered the floor with the map, we where playing in my eating room separated by a curtain from the living room, when the giants attacked i pulled back the curtain and we played on the floor all over the map - great fun. I wrote an encounter at the storval stairs
Details:
The sandpoint attack was fun and a great way to show the PC's advancement, defeating a hand full of goblins in BO and now giants and a dragon in the same place. Both groups befriended a mammoth at the storval stairs (after killing its giant rider) one group thought about awaking and training it as a ranger :-) the others made Titus Scarnetti build a stable for it :-) The payoff of the Scarnetti-Arc was quite nice, the high point of FotSG was Mokmurian, the fight was quite memorable and well-written, the library guardian was a fun rolrole-plaing encounter
Overall: Solid and good old school feel but not that memorable

This one is very good but my PCs are not fans of very large dungeons... The plot on this one is quite simple but the encounters are quite coloful. The enemies are quite creative and there are some pretty cool encounters with the kind of adversaries you see once in a campaign. So all in all a great adventure. I'm taking one star away on a personal preference of lots-of-cool-locations- adventurers