code: function initBook(root, opts) {
      var book = new Book(root, opts);
      var extensionToUse = '.md';
  
      var chaptersPaths = function(chapters) {
          return _.reduce(chapters || [], function(accu, chapter) {
              var o = {
                  title: chapter.title
              };
              if (chapter.path) o.path = chapter.path;
  
              return accu.concat(
                  [o].concat(chaptersPaths(chapter.articles))
              );
          }, []);
      };
  
      book.log.info.ln('init book at', root);
      return fs.mkdirp(root)
      .then(function() {
          book.log.info.ln('detect structure from SUMMARY (if it exists)');
          return book.parseSummary();
      })
      .fail(function() {
          return Q();
      })
      .then(function() {
          var summary = book.summaryFile || 'SUMMARY.md';
          var chapters = book.summary.chapters || [];
          extensionToUse = path.extname(summary);
  
          if (chapters.length === 0) {
              chapters = [
                  {
                      title: 'Summary',
                      path: 'SUMMARY'+extensionToUse
                  },
                  {
                      title: 'Introduction',
                      path: 'README'+extensionToUse
                  }
              ];
          }
  
          return Q(chaptersPaths(chapters));
      })
      .then(function(chapters) {
          // Create files that don't exist
          return Q.all(_.map(chapters, function(chapter) {
              if (!chapter.path) return Q();
              var absolutePath = path.resolve(book.root, chapter.path);
  
              return fs.exists(absolutePath)
              .then(function(exists) {
                  if(exists) {
                      book.log.info.ln('found', chapter.path);
                      return;
                  } else {
                      book.log.info.ln('create', chapter.path);
                  }
  
                  return fs.mkdirp(path.dirname(absolutePath))
                  .then(function() {
                      return fs.writeFile(absolutePath, '# '+chapter.title+'\n');
                  });
              });
          }));
      })
      .then(function() {
          book.log.info.ln('initialization is finished');
      });
  }
docs: Initialize folder structure for a book Read SUMMARY to created the right chapter