MUSIC BY PHILIP GLASS <i> by Philip Glass (Harper & Row: $12.95, illustrated)</i>

This readable memoir focuses on the creation of Philip Glass’ celebrated “portrait opera� trilogy (“Einstein on the Beach,� “Satyagraha,� “Akhnaten�), which ranks among the seminal works of late 20th-Century music. Glass explains the origins of his complex, Minimalist style (although the examples he offers will be lost on anyone who can’t sight read music) and recounts the problems of writing and staging a new opera. The financial difficulties often prove more daunting than the technical/aesthetic ones: Glass supported his family by working as a cab driver and a plumber while he was completing “Einstein on the Beach.� As none of the operas has been staged in Los Angeles, the book enhances the pleasure of listening to the CDs by explaining some of the visuals that accompany the music.