This stack trace from the conversion plugin gives some better information: Converti libro 1 di 1 (Hyperion) Traceback (most recent call last): File "site-packages/calibre/customize/zipplugin.py", line 42, in get_resources File "lib/python2.7/zipfile.py", line 931, in read File "lib/python2.7/zipfile.py", line 957, in open File "lib/python2.7/zipfile.py", line 905, in getinfo KeyError: "There is no item named u'translations/it.mo' in the archive" Traceback (most recent call last): File "site-packages/calibre/customize/zipplugin.py", line 42, in get_resources File "lib/python2.7/zipfile.py", line 931, in read File "lib/python2.7/zipfile.py", line 957, in open File "lib/python2.7/zipfile.py", line 905, in getinfo KeyError: "There is no item named u'translations/it.mo' in the archive" Resolved conversion options calibre version: 1.12.0 {'asciiize': False, 'author_sort': None, 'authors': None, 'base_font_size': 0.0, 'book_producer': None, 'change_justification': u'original', 'chapter': u"//*[((name()='h1' or name()='h2') and re:test(., '\\s*((chapter|book|section|part)\\s+)|((prolog|prologue|epilogue)(\\s+|$))', 'i')) or @class = 'chapter']", 'chapter_mark': u'pagebreak', 'comments': None, 'cover': u'/var/folders/v1/3_pgkn4j2gd69w23q2_glvm40000gn/T/calibre_1.12.0_tmp_8GyoMq/PivoIe.jpeg', 'debug_pipeline': None, 'dehyphenate': True, 'delete_blank_paragraphs': True, 'disable_font_rescaling': False, 'dont_split_on_page_breaks': False, 'duplicate_links_in_toc': False, 'embed_all_fonts': False, 'embed_font_family': None, 'enable_heuristics': False, 'epub_flatten': False, 'epub_inline_toc': False, 'epub_toc_at_end': False, 'expand_css': False, 'extra_css': None, 'extract_to': None, 'filter_css': u'', 'fix_indents': True, 'flow_size': 260, 'font_size_mapping': None, 'format_scene_breaks': True, 'html_unwrap_factor': 0.4, 'input_encoding': None, 'input_profile': , 'insert_blank_line': False, 'insert_blank_line_size': 0.5, 'insert_metadata': False, 'isbn': None, 'italicize_common_cases': True, 'keep_ligatures': False, 'kepub_clean_markup': True, 'kepub_hyphenate': True, 'kepub_replace_lang': True, 'language': None, 'level1_toc': None, 'level2_toc': None, 'level3_toc': None, 'line_height': 0.0, 'linearize_tables': False, 'margin_bottom': 5.0, 'margin_left': 5.0, 'margin_right': 5.0, 'margin_top': 5.0, 'markup_chapter_headings': True, 'max_toc_links': 50, 'minimum_line_height': 120.0, 'no_chapters_in_toc': False, 'no_default_epub_cover': False, 'no_inline_navbars': False, 'no_svg_cover': False, 'output_profile': , 'page_breaks_before': u"//*[name()='h1' or name()='h2']", 'prefer_metadata_cover': False, 'preserve_cover_aspect_ratio': False, 'pretty_print': True, 'pubdate': None, 'publisher': None, 'rating': None, 'read_metadata_from_opf': u'/var/folders/v1/3_pgkn4j2gd69w23q2_glvm40000gn/T/calibre_1.12.0_tmp_8GyoMq/XNmthT.opf', 'remove_fake_margins': True, 'remove_first_image': False, 'remove_paragraph_spacing': False, 'remove_paragraph_spacing_indent_size': 1.5, 'renumber_headings': True, 'replace_scene_breaks': u'', 'search_replace': '[]', 'series': None, 'series_index': None, 'smarten_punctuation': True, 'sr1_replace': None, 'sr1_search': None, 'sr2_replace': None, 'sr2_search': None, 'sr3_replace': None, 'sr3_search': None, 'start_reading_at': None, 'subset_embedded_fonts': False, 'tags': None, 'timestamp': None, 'title': None, 'title_sort': None, 'toc_filter': None, 'toc_threshold': 6, 'toc_title': None, 'unsmarten_punctuation': False, 'unwrap_lines': True, 'use_auto_toc': False, 'verbose': 2} InputFormatPlugin: EPUB Input running on /var/folders/v1/3_pgkn4j2gd69w23q2_glvm40000gn/T/calibre_1.12.0_tmp_8GyoMq/RbDX2h.epub Found HTML cover OEBPS/titlepage.xhtml Parsing all content... Parsing OEBPS/Epilogo.html ... Parsing OEBPS/Capitolo 5.html ... Parsing OEBPS/Dedica.html ... Parsing OEBPS/Prologo.html ... Parsing OEBPS/_license0.xhtml ... Parsing OEBPS/Capitolo 6.html ... Parsing OEBPS/Capitolo 2.html ... Parsing OEBPS/jacket.xhtml ... Parsing OEBPS/Capitolo 1.html ... Parsing OEBPS/Capitolo 3.html ... Parsing OEBPS/Capitolo 6.html ... Parsing OEBPS/Capitolo 2.html ... Parsing OEBPS/Capitolo 3.html ... Parsing OEBPS/Capitolo 5.html ... Parsing OEBPS/Capitolo 1.html ... Parsing OEBPS/Capitolo 4.html ... Parsing OEBPS/Copertina.xhtml ... Parsing OEBPS/Text/template2.css ... Parsing OEBPS/Text/Copyright.xhtml ... Parsing OEBPS/Frontespizio.xhtml ... Parsing OEBPS/titlepage.xhtml ... Parsing OEBPS/Capitolo 4.html ... Parsing OEBPS/template.css ... Removing duplicate manifest item with id: id5 Removing duplicate manifest item with id: id1 Removing duplicate manifest item with id: id4 Removing duplicate manifest item with id: id0 Removing duplicate manifest item with id: id3 Removing duplicate manifest item with id: id2 Reading TOC from NCX... Merging user specified metadata... Detecting structure... Removed existing jacket Flattening CSS and remapping font sizes... Source base font size is 11.04000pt Removing fake margins... Found 20 items of level: div_1 Found 18 items of level: div_2 Found 14 items of level: p_2 Found 4992 items of level: p_3 Ignoring level p_2 div_1 left margin stats: Counter({u'': 10}) div_1 right margin stats: Counter({u'': 10}) div_2 left margin stats: Counter({u'': 8}) div_2 right margin stats: Counter({u'': 8}) p_3 left margin stats: Counter({u'11px': 4505, u'0': 317, u'23px': 170}) p_3 right margin stats: Counter({u'11px': 4506, u'0': 316, u'23px': 170}) Cleaning up manifest... Trimming unused files from manifest... Trimming u'OEBPS/titlepage.xhtml' from manifest Python function terminated unexpectedly: [Errno 21] Is a directory: u'/private/var/folders/v1/3_pgkn4j2gd69w23q2_glvm40000gn/T/calibre_1.12.0_tmp_8GyoMq/ZId4W__epub_container/kte-css/hyphenation.css' Creating KePub Output... Rescaling image from 565x800 to 484x686 OEBPS/img/_img_license0.png Rescaling image from 550x843 to 447x686 cover.jpeg Rescaling image from 550x610 to 512x568 OEBPS/Images/fr_fmt.jpg Splitting markup on page breaks and flow limits, if any... Looking for large trees in OEBPS/Epilogo.html... No large trees found Looking for large trees in OEBPS/Dedica.html... No large trees found Looking for large trees in OEBPS/Prologo.html... No large trees found Looking for large trees in OEBPS/_license0.xhtml... No large trees found Looking for large trees in OEBPS/Capitolo%206.html... No large trees found Looking for large trees in OEBPS/Capitolo%202.html... No large trees found Looking for large trees in OEBPS/Capitolo%201.html... No large trees found Looking for large trees in OEBPS/Capitolo%203.html... No large trees found Looking for large trees in OEBPS/Capitolo%205.html... No large trees found Looking for large trees in OEBPS/Capitolo%204.html... No large trees found Looking for large trees in OEBPS/Copertina.xhtml... No large trees found Looking for large trees in OEBPS/Text/Copyright.xhtml... No large trees found Looking for large trees in OEBPS/Frontespizio.xhtml... No large trees found Copying file '/var/folders/v1/3_pgkn4j2gd69w23q2_glvm40000gn/T/calibre_1.12.0_tmp_8GyoMq/Kdco2P_KePubOutputPluginInfo' to '/private/var/folders/v1/3_pgkn4j2gd69w23q2_glvm40000gn/T/calibre_1.12.0_tmp_8GyoMq/ZId4W__epub_container' as 'plugininfo.kte' {'smarten_punctuation': False, 'extended_kepub_features': True, 'replace_lang': True, 'hyphenate': True, 'clean_markup': True} KoboTouchExtended:common:modify_epub:Found cover image ID 'cover' KoboTouchExtended:common:modify_epub:Setting cover-image property Forcing cleanup for file OEBPS/Capitolo 1.html Forcing cleanup for file OEBPS/Capitolo 2.html Forcing cleanup for file OEBPS/Capitolo 3.html Forcing cleanup for file OEBPS/Capitolo 4.html Forcing cleanup for file OEBPS/Capitolo 5.html Forcing cleanup for file OEBPS/Capitolo 6.html Forcing cleanup for file OEBPS/Copertina.xhtml Forcing cleanup for file OEBPS/Dedica.html Forcing cleanup for file OEBPS/Epilogo.html Forcing cleanup for file OEBPS/Frontespizio.xhtml Forcing cleanup for file OEBPS/Prologo.html Forcing cleanup for file OEBPS/Text/Copyright.xhtml Forcing cleanup for file OEBPS/_license0.xhtml Forcing cleanup for file titlepage.xhtml Cleaning markup for file OEBPS/Capitolo 1.html Cleaning markup for file OEBPS/Capitolo 2.html Cleaning markup for file OEBPS/Capitolo 3.html Cleaning markup for file OEBPS/Capitolo 4.html Cleaning markup for file OEBPS/Capitolo 5.html Cleaning markup for file OEBPS/Capitolo 6.html Cleaning markup for file OEBPS/Copertina.xhtml Cleaning markup for file OEBPS/Dedica.html Cleaning markup for file OEBPS/Epilogo.html Cleaning markup for file OEBPS/Frontespizio.xhtml Cleaning markup for file OEBPS/Prologo.html Cleaning markup for file OEBPS/Text/Copyright.xhtml Cleaning markup for file OEBPS/_license0.xhtml Cleaning markup for file titlepage.xhtml Traceback (most recent call last): File "/Applications/calibre.app/Contents/Resources/Python/lib/python2.7/site.py", line 208, in main return run_entry_point() File "/Applications/calibre.app/Contents/Resources/Python/lib/python2.7/site.py", line 114, in run_entry_point return getattr(pmod, func)() File "site-packages/calibre/utils/ipc/worker.py", line 189, in main File "site-packages/calibre/gui2/convert/gui_conversion.py", line 31, in gui_convert_override File "site-packages/calibre/gui2/convert/gui_conversion.py", line 25, in gui_convert File "site-packages/calibre/ebooks/conversion/plumber.py", line 1189, in run File "calibre_plugins.koboconversion.conversion.kepub_output", line 98, in convert File "calibre_plugins.koboconversion.common", line 73, in modify_epub File "calibre_plugins.koboconversion.container", line 120, in copy_file_to_container File "site-packages/calibre/ebooks/oeb/polish/container.py", line 679, in generate_item IOError: [Errno 21] Is a directory: u'/private/var/folders/v1/3_pgkn4j2gd69w23q2_glvm40000gn/T/calibre_1.12.0_tmp_8GyoMq/ZId4W__epub_container/kte-css/hyphenation.css'