I tried it out. First issue is that on multiple ePubs where the epubcheck v5.3.0 did not indicate any errors, epubveri came up with the following errors:
Code:
C:\Users\<user>\Desktop>D:\builder\epubveri\target\release/epubveri monospace_test.epub
ERROR RSC-005: value of attribute "property" is invalid (must not be empty) [OEBPS/content.opf]
INFO OPF-088: epub:type value 'frontmatter' is not in the default vocabulary [OEBPS/Text/nav.xhtml]
ERROR OPF-096: non-linear content 'OEBPS/Text/nav.xhtml' is not reachable from the reading order [OEBPS/content.opf]
— 2 error(s), 0 warning(s): INVALID
Near as I can tell, the only property in the .opf file is not empty(
*) and nav.xhtml is properly flagged as non-linear and so should not be accessible from the reading order. And the info about frontmatter? Near as I can tell, it is one of the default items according to the latest ePub3 spec under section 2: Document Partitions.
Code:
<meta property="dcterms:modified">2026-03-02T09:56:05Z</meta>
I tried a couple of other ePubs and got a mix of valid and invalid error messages. Some of the messages were ones that earlier versions of epubcheck would generate but all the ones I am aware of were fixed in epubcheck v5.3.0 back in Sept., 2025.
I suspect I should have dumped my old Rust install. It took more effort to update than a simple install would have taken.