In the same directory where I have the book there is my file containing variables and scheme functions, usefullibrary.ly .
In 2.14.2 lilypond-book searched for the files included by score.ly relative to book.lytex (so I used to write \include "usefullibrary.ly" in dir/subdir/score.ly),
now it searches for them relative to score.ly (so I have to write \include "../../usefullibrary.ly").
It's no killing issue for me, I just wanted to ask if this change was a feature or a bug.