fixed layout document body margin reset to zero to ensure user stylesheet doesn't set default 8px margin all around, see
MODIFY
js/views/one_page_view.js
js/views/one_page_view.js
@@ -377,6 +377,10 @@ var OnePageView = function (options, classes, enableBookStyleOverrides, reader)
_$epubBody = undefined;
} else {
_$epubBody = $("body", _$epubHtml);
+
+ if (!_enableBookStyleOverrides) { // fixed layout
+ _$epubBody.css("margin", "0"); // ensures 8px margin default user agent stylesheet is reset to zero
+ }
}
//_$epubHtml.css("overflow", "hidden");

fixed layout document body margin reset to zero to ensure user stylesheet doesn't set default 8px margin all around, see https://github.com/readium/readium-js-viewer/issues/673#event-1345872614