“Mathias Sandorf” is a novel by French 19th century adventure and science fiction writer Jules Verne. I read it as a teenager, and haven't reread it for years! I've also seen a TV series based on the novel (it had a less gruesome ending). Verne explicitly intended the novel to be a tribute to Alexandre Dumas and “The Count of Monte Cristo”, but this is actually somewhat unfortunate, since it reveals a central part of the plot in advance.
The story is set in Austria-Hungary and around the Mediterranean. Verne was fairly “progressive” and this is reflected in the novel, with the heroes being Hungarian democratic revolutionaries in the tradition of 1848 rising up against the Austrian monarchy and the Hungarian aristocracy. The revolutionary cell, led by Mathias Sandorf, is betrayed and its members killed. 15 years later a mysterious character named Dr Antekirtt starts to systematically hunt down and kill those who betrayed the patriotic resistance. If you know your Dumas, you know exactly how the story ends: Antekirtt turns out to be none other than Sandorf himself, back from the dead and bent on revenge of the “cruel and unusual” kind.
Although strongly inspired by Dumas, the novel also has typical Vernesque themes. In keeping with Verne's “pro-technology” perspective, Dr Antekirtt is a scientist roaming the Mediterranean in an advanced submarine. He also disposes of his enemies in surprisingly high tech fashion. Antekirtt is obviously based on Captain Nemo of Verne's earlier novels “Twenty Thousand Leagues Under the Sea” and “The Mysterious Island”. Both the doctor and the captain are liberation fighters driven by personal hatred and endowed with u-boats.
If you like near-epic adventure novels, this might be for you. Also interesting if you are a Verne aficionado, or like “Eastern” and Southern Europe. If it beats the Count of Monte Cristo is perhaps another matter entirely…