Oh, and the ebook-convert log, as required when asking a question (but everything's normal here)
Code:
iliakan> /Applications/calibre.app/Contents/MacOS/ebook-convert book.html book.epub --embed-all-fonts --max-toc-links 0 --level1-toc '//h:h2' --level2-toc '//h:h3'
1% Converting input to HTML...
InputFormatPlugin: HTML Input running
on /Users/iliakan/epub/book.html
Language not specified
Creator not specified
Building file list...
Normalizing filename cases
Rewriting HTML links
34% Running transforms on ebook...
Merging user specified metadata...
Detecting structure...
Auto generated TOC with 0 entries.
Flattening CSS and remapping font sizes...
Source base font size is 12.00000pt
Removing fake margins...
Cleaning up manifest...
Trimming unused files from manifest...
Creating EPUB Output...
67% Running EPUB Output plugin
Splitting markup on page breaks and flow limits, if any...
Looking for large trees in book.html...
No large trees found
Generating default cover
This EPUB file has no Table of Contents. Creating a default TOC
EPUB output written to /Users/iliakan/epub/book.epub
Output saved to /Users/iliakan/epub/book.epub