Otherwise it's not offered to open its files. Mageia is adding the following mimes: http://svnweb.mageia.org/packages/cauldron/fbreader/current/SPECS/fbreader.spec?revision=522451&view=markup application/epub+zip;application/rtf;application/x-mobipocket-ebook;application/x-fictionbook+xml;text/html;application/xhtml+xml;
10 Jul 2014; Andrey Grozin <grozin@gentoo.org> -fbreader-0.99.4.ebuild, +fbreader-0.99.4-r2.ebuild, +files/fbreader-0.99.4-mimetypes.patch, +files/fbreader-0.99.4-qreal-cast.patch: Added casts to qreal (bug #515698), thanks to William Throwe <wtt6@cornell.edu>; added mimetypes to .desktop (bug #516794); depend on qtcore[ssl] (bug #462044); added -j1 (bug #484516)