Hi Troxio, welcome to Chrons.
Technically you can read them before Sword and Midnight, although the four books are based around the Rigante people, Ravenheart and Stormrider are set hundreds of years later than the first two, However, certain events from the first two are mentioned in the last two and may spoil the reading of the first two as you'll know what happens.
Anyway, hope you enjoy them, Gemmells books are first class
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