Today's free book is Great Opera Stories by Millicent Schwab Bender (1912). For the table of contents, check at the bottom of this post below the image.
The book is available at Project Gutenberg (I have not checked for other online sources).
Table of Contents
Children of Kings
Haensel and Gretel
The Master Singers
Lohengrin, the Knight of the Swan
The Flying Dutchman
Tannhäuser, the Minstrel Knight