Joe, I just checked the notes accompanying the A Song for Every Season LP set. They have an appendix with the words of the 15 (!) songs not included in the A Song for Every Season book, but unfortunately just the words, without a melody.

And the book also has a lot of songs that aren't on the LPs. If I have counted correctly, the LPs have 45 songs and the book has 47. So if 15 songs are on the LPs but not in the book, they have a common set of 30 songs, and 17 songs in the book are not on the LPs.