As it is a result, there is no problem in understanding the events and to recognize the characters but it's true that if we start with this book, it is not even worth it.
There are two plots: the past Rouletabille and return Larsan.
Regarding the first point, it is very well taken but I'm disappointed not to find the journalist of the first volume, prodigious, mischievous, a little naive ... Here we have a nervous, anxious, dark, constantly on guard ...
For the second point, the novel is steeped in the absence and presence of Larsan ... It is there, close to them, they feel his eyes ... fear is present throughout the novel. They must find out where it is and get rid once and for all.
This constant voltage is very disturbing, that dark reading the passages are long, they are all worried constantly ... after a while, I wanted some sun, something else ... one joke.
Many long passages in history as the description of the Fort of Hercules with a plan ... and throughout the novel, we are referred to the plan ... This lack of dialogue, pace.
I liked when I was in high school, it was my period "detective story" but now the sauce takes longer.