Shiva Purana is one among the most important Puranas and narrates the stories associated with Hindu God Shiva. Reading Shiv Puran on Mondays and other auspicious days associated with Shiva is considered highly rewarding. 
The Puran is also read during the Shravan Mahina (July – August), as it is dedicated to Shiva. Shiva Puran in Hindi is provided by Ved Puran website. You can read it online in Hindi but there is no download option.
You can read Shiva Purana in Hindi here at Ved Puran.