Some books in English on shaiva sidhdhantha

• Tirumantiram, a Tamil scriptural classic / by Tirumular ; Tamil text with English translation and notes by B. Natarajan. 
  Publisher: Ramakrishna Math
• Periya puranam, a Tamil classic on the great Saiva saints of South India / by Sekkizhaar ; condensed English version by G. Vanmikanathan.
  Publisher: Ramakrishna Math
• Introduction & history of Saiva Siddhanta./ by K. Subramania Pillai
  Annamalai University
• Pathway to God through Tamil literature, by G. Vanmikanathan. Publisher: Delhi Tamil Sangam publications
• The Thirukkural / English rendering by G. Vanmikanathan.
• Maanickavaacagar, poet and mystic; an original interpretation of the Tiruvaacagam, by G. Vanmikanathan.
  Publisher: Thirukurral prachar sangh
• Thiruvilayaadal puraanam : sixty four leelas of Lord Somsundareswara of Madurai / by S. Swaminathan.
  Publisher: Sri Saiva Maha peetam
• The greatness of S'iva : Mahimnastava of Puspadanta by Jagannatha. The metaphysics of the Saiva Siddhanta system / by K. Subramania Pillai.
• The metaphysics of the Saiva Siddhanta system / by K. Subramania Pillai. Publisher: South Indian Saiva Siddhanta Publications.

The above list is courtesy of Mr. Giridhar.