Thanks for the hint. I did that, however, but it failed with:
ERROR: Conversion Error: <b>Failed</b>: Convert book 1 of 1 (The Grapes of Wrath)
Convert book 1 of 1 (The Grapes of Wrath)
Resolved conversion options
calibre version: 0.7.37
{'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(., 'chapter|book|section|part|prologue|epilogue\\s+', 'i')) or @class = 'chapter']",
'chapter_mark': u'pagebreak',
'comments': None,
'cover': 'c:\\users\\lee\\appdata\\local\\temp\\calibre_0.7 .37_tmp_vit7yl\\calibre_0.7.37_wk4wwt.jpeg',
'debug_pipeline': None,
'disable_font_rescaling': False,
'dont_split_on_page_breaks': False,
'epub_flatten': False,
'extra_css': None,
'extract_to': None,
'flow_size': 260,
'font_size_mapping': None,
'footer_regex': u'(?i)(?<=<hr>)((\\s*<a name=\\d+></a>((<img.+?>)*<br>\\s*)?\\d+<br>\\s*.*?\\s*)|(\\s* <a name=\\d+></a>((<img.+?>)*<br>\\s*)?.*?<br>\\s*\\d+))(?=<br>)' ,
'header_regex': u'(?i)(?<=<hr>)((\\s*<a name=\\d+></a>((<img.+?>)*<br>\\s*)?\\d+<br>\\s*.*?\\s*)|(\\s* <a name=\\d+></a>((<img.+?>)*<br>\\s*)?.*?<br>\\s*\\d+))(?=<br>)' ,
'html_unwrap_factor': 0.4,
'input_encoding': None,
'input_profile': <calibre.customize.profiles.InputProfile object at 0x056D6CD0>,
'insert_blank_line': False,
'insert_metadata': False,
'isbn': None,
'keep_ligatures': False,
'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,
'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': <calibre.customize.profiles.NookColorOutput object at 0x056E6090>,
'page_breaks_before': u"//*[name()='h1' or name()='h2']",
'prefer_metadata_cover': False,
'preprocess_html': True,
'preserve_cover_aspect_ratio': False,
'pretty_print': True,
'pubdate': None,
'publisher': None,
'rating': None,
'read_metadata_from_opf': 'c:\\users\\lee\\appdata\\local\\temp\\calibre_0.7 .37_tmp_vit7yl\\calibre_0.7.37_zbw47m.opf',
'remove_first_image': False,
'remove_footer': False,
'remove_header': False,
'remove_paragraph_spacing': False,
'remove_paragraph_spacing_indent_size': 1.5,
'series': None,
'series_index': None,
'smarten_punctuation': False,
'tags': None,
'timestamp': None,
'title': None,
'title_sort': None,
'toc_filter': None,
'toc_threshold': 6,
'use_auto_toc': False,
'verbose': 2}
InputFormatPlugin: MOBI Input running
on C:\Users\Lee\Calibre Library\John Steinbeck\The Grapes of Wrath (253)\The Grapes of Wrath - John Steinbeck.mobi
Extracting text...
Adding anchors...
Extracting images...
Cleaning up HTML...
Parsing HTML...
Converting style information to CSS...
Creating OPF...
Parsing all content...
Parsing The_Grapes_of_Wrath.html ...
Forcing The_Grapes_of_Wrath.html into XHTML namespace
Parsing styles.css ...
Generating default TOC from spine...
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
Cleaning up manifest...
Trimming unused files from manifest...
Parsing stylesheet.css ...
Trimming 'images/00001.jpg' from manifest
Trimming 'images/00002.jpg' from manifest
Creating EPUB Output...
Splitting on page-break
Splitting on page-break
Looking for large trees in The_Grapes_of_Wrath.html...
Found large tree #1
Splitting...
Split point: {http://www.w3.org/1999/xhtml}div /*/*[2]/*[5539]
Split tree too small
Splitting...
Split point: {http://www.w3.org/1999/xhtml}div /*/*[2]/*[5538]
Split tree too small
Splitting...
Python function terminated unexpectedly
Could not find reasonable point at which to split: The_Grapes_of_Wrath.html Sub-tree size: 1843 KB (Error Code: 1)
Traceback (most recent call last):
File "site.py", line 103, in main
File "site.py", line 85, in run_entry_point
File "site-packages\calibre\utils\ipc\worker.py", line 107, in main
File "site-packages\calibre\gui2\convert\gui_conversion.py", line 24, in gui_convert
File "site-packages\calibre\ebooks\conversion\plumber.py", line 965, in run
File "site-packages\calibre\ebooks\epub\output.py", line 169, in convert
File "site-packages\calibre\ebooks\oeb\transforms\split.py", line 56, in __call__
File "site-packages\calibre\ebooks\oeb\transforms\split.py", line 66, in split_item
File "site-packages\calibre\ebooks\oeb\transforms\split.py", line 188, in __init__
File "site-packages\calibre\ebooks\oeb\transforms\split.py", line 392, in split_to_size
File "site-packages\calibre\ebooks\oeb\transforms\split.py", line 392, in split_to_size
File "site-packages\calibre\ebooks\oeb\transforms\split.py", line 385, in split_to_size
calibre.ebooks.oeb.transforms.split.SplitError: Could not find reasonable point at which to split: The_Grapes_of_Wrath.html Sub-tree size: 1843 KB