The load function read progress.epub_loc and progress.progress, neither of
which BookProgressRead carries, so resuming never worked and every open
started at page one. Read epub_cfi and percentage instead.
Fail loudly when the book cannot be fetched. The previous version caught
everything and returned {status, error} that nothing consumed, so a missing
book produced a reader sitting on its spinner forever. Check response.ok
before parsing too: fetch resolves on a 404, and arrayBuffer() happily
returns the error page, which only surfaced later as an opaque epub parse
error.
Give the reader a working sidebar, a theme that survives the book's own
CSS, and an error state with a retry. The theme is registered rather than
applied as bare overrides because most EPUBs ship their own body colours
and win otherwise, which is why the page stayed white against a dark UI.
patrick
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