The title is part of a Sanskrit chant/prayer, from the Brihadaranyaka Upanishad, that goes; And you can see Tamso Ma Jyotirgamaya in Hindi, and English
असतो मा साद गमय, तमसो मा ज्योतिर् गमय, मृत्योर मा अमृतम् गमय
You can also see Vakratunda Mahakaya
(Asato Ma Sad Gamaya, Tamaso Ma Jyotir Gamaya, Mrityor Ma Amritam Gamaya)
Tomaso can be said to be a companion volume to Asato Ma Sadgamaya (असतो मा सद्गमय) and Mrityorma Amritam Gamaya (मृत्योर्मा अमृतं गमय), though they are eras apart and have no other connection with one another. It exists in audio form and as a partial e-book (the first six chapters).