"Son of a Wanted Man" by Louis L'Amour

Mike Bastian is the adopted son of Ben Curry, an aging outlaw king.  Curry expects Mike to take over his lawless empire so that he can retire with his secret family and live out the rest of his days in peace.  But Mike isn't sure he's interested.  When others in Curry's organization sense this, they try to take over themselves.  The ensuing violence and outlawry draws the attention of two lawmen, Borden Chantry and Tyrel Sackett, and Mike finally has to take a side and make his stand.
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