I discovered this book after I read Jean's wonderful Extending Lilypond webpage. I tried to access the URL but it didn't work. I've only found the Github repository of the book but it is really difficult to read portions of it in this state. Sometimes even referenced links in the repository display 404s.
Is the website/project dead for good or it will be back eventually? I'm really looking to get more serious with Scheme and any resources I can find certainly help.
Best,
Dimitris