Many of the events it describes, such as the Lisbon earthquake and the public burning of heretics that followed, were recent news items at the time the book was written, but this doesn't make it appear dated. It works as satire because it is so firmly based in human nature.
There is a lot of cruelty and savagery in the story. Horrible things happen to Candide and to those around him, and he himself kills a couple of people, although in self-defence. But all this is described in near-farcical terms, so that the horrors strike you almost as an afterthought, in a double take; you find yourself thinking, "This is absurd", and then you realise that such things really do happen.
This double-take effect is enhanced by the abundance of impossible coincidences that occur, making the narrative into a fable. There are other impossibilities too. The characters are like those in a Walt Disney cartoon; they are hanged or mutilated or burnt alive, yet they don't die but reappear later—horribly disfigured and at first unrecognisable, but still alive.
The characters are also cartoon-like in not developing psychologically, no matter what they experience. They are two-dimensional mouthpieces for philosophical views. The prime example is Candide's tutor Pangloss, who maintains his optimistic philosophy (based on Leibnitz) throughout all the misfortunes he suffers. Only Candide himself is a partial exception; he remains almost (but not quite) as kindly and good-natured throughout as he was at the beginning of his adventures, but he does lose his naïvety and gains a measure of worldly wisdom by the end.
This e-book version doesn't credit the English translation to anyone but from the style I think it is by Tobias Smollet, who translated all Voltaire's works in the 1760s.