this is a tool to validate IDPF EPUB files, version 2.0 and later. It can detect many types of errors in EPUB. OPF and OPS mark-up, and internal reference consistency are checked. you can purchase iap for write EPUB: 1、New Blank epub ,New epup from txt or chm,Batch create epub from txt/chm ； 2、add blank or exists files to epub,include: *.html,*.htm,*.xhtml,*.png,*.svg,*.jpeg,*.jpg,*.bmp,*.otf,*.txt,*.css;adding nested directories to epub; 3、edit toc、opf、html file content，preview html 4、create new directory、delete file or directory； 5、drag and drop to move toc、 edit toc name； 6、edit epub metadata；