Reading through this, my first thought is that it is not an adventure, it's a whole campaign... or at least the start of one. Maybe that is right: the whole thing is, despite being set up for starting characters (levels 1-2), it's of epic proportions, sweeping the characters up in the footsteps of legends and into the middle of a war.
There is a lot of background detail for the DM, and indeed the players, to absorb. If the characters are native to the land of Arthad (0one's campaign setting), they would know the underlying legends and fortunately these are summarised in the first handout - probably best given to the players before the game begins so that they can absorb it in advance. They would also benefit from reading the Heroes and Magic Sourcebook which explains the way in which the Arthad setting works in more detail. Arthad is low-magic, and clerics have a somewhat difficult time as all the gods have departed... fortunately their spells still work, just a bit differently.
Alternatively, you may prefer to use the adventure in your own world, but this will require quite a lot of amendment to the background and is perhaps not a good idea. One possibility is to 'summon' the characters from another world as the predestined 'Heroes' who hopefully will save the day (a possibility not described in the product, but one which occurred to me while reading it!).
Basically, when the gods left Arthad, it was not peaceful. The leading evil god was in fact smashed into 7 pieces, which have been kept at bay by powerful magics... which is, of course, fading now. One of these shards is now active within the leader of the nomads of the east, who are winding up in tremendous strength to invade the west. All that stands in their way is the citidel built to guard the main pass in the mountain range separating east and west, and it is here that the action begins.
The characters start off by being sent to visit a reclusive clerical order who might be persuaded to help, but along the way they can pick up clues that will show them both the identity of the traitor within the citadel and an inkling of how the vast nomad horde might be defeated by bringing back the spirit of an 8,000-year old general. As the siege commences, they have the opportunity to act as a kind of 'special forces' unit (generally the best sort of role for a bunch of PCs when all-out war is raging in a game), and even to venture into the Afterlife (once they find the way in) to look for the general's spirit.
The whole thing is presented in several chapters, each subdivided into 'Events' and 'Locations.' The Events may happen in the sequence presented or may be triggered by something else - character action, time, visit to a Location - while the Locations are places that it's likely the characters will visit and each contains descriptions and possible clues as to what they ought to do. While this sounds quite open, it needs to be run with care as it would be very easy for the characters to miss discovering what actions they are expected to take - not all of the clues are clear even when you have the whole adventure, let alone when you are one of the players!
Presentation throughout is of the customary high visual standard that is normal with 0one Games, although proof-reading by a native English speaker might have helped catch some of the errors in the text. Overall, it is an exciting adventure, and refreshing to have one in which low-level characters are more than mere pawns in matters of such epic scale.Rating: [4 of 5 Stars!]