Book Isle duplicate imports: handle EPUB and PDF versions of one book

English translation of the Chinese original, translated on 2026-10-23. The article body uses automated translation; app descriptions, historical reading notes and video subtitles receive separate editorial checks. Original publication dates, attribution, code and version notes are retained.

Keeping EPUB and PDF for one book is common: EPUB suits continuous phone reading while PDF preserves pages and figures. Book Isle's import preview helps identify duplicates or multiple formats, but you still confirm editions. Use files known to belong together to practice retaining primary and alternate formats.

Define what “the same book” means first

Prepare an EPUB and PDF and compare title, author, edition, and text. They should be the same edition or editions you deliberately want managed together. Same titles with different authors, translations, or abridgments should not merge by name alone. Retain originals for later checks.

The primary format opens for reading by default; an alternate is another file retained under that record. They are not conversion outputs and do not turn EPUB layout into PDF. For comparing different translations, two clearly named records usually make notes and source identification easier.

Import your preferred regular format first

Select EPUB through Local File Import, complete the preview and import, and open a chapter. Return to the shelf and long-press to enter Book Details, checking Primary Format and Available Formats. Usually only the imported format is present at this point. Note title and progress as a reference for the merge.

If page lookup is your main use, import PDF first. Choose the primary format for its purpose, not because an extension is inherently superior. PDF may suit tables and formulas, while reflowable EPUB often suits novels. This demonstrates an operation sequence without requiring one default format for every book.

Inspect the second import preview carefully

Select the other format and inspect whether Import Preview marks it as new, merge format, skip duplicate, or possible duplicate. If a same-book merge is offered, confirm the existing target before saving as an alternate or promoting it to primary. Labels vary by version; read import, merge, and skip totals before proceeding.

Do not automatically merge every “Possible Duplicate.” Depending on the interface, choose new-book import, merge, or skip. If edition relationships are uncertain, separate records are easier to compare later. Import coordination offers clues; similar size, title, or author cannot prove identical text.

Verify that both formats appear in details

Open the original book's details and check that Available Formats includes EPUB and PDF, noting which is primary. If Switch Primary Format to PDF or an equivalent button exists, switch and open it to confirm the PDF reader appears. Switch back to EPUB and check text and reading behavior.

Verify three results separately: the file exists, the file reads, and the record is correct. “Merge successful” alone is insufficient; an alternate file may be damaged or protected. Handle one group first and confirm behavior before scaling up, avoiding discovery after a bulk operation that different editions were combined.

Do not expect positions to align automatically between formats

EPUB chapter and text positions differ from fixed PDF pages. After changing the primary format, do not assume page ten maps to page ten or a precise selection shares the same coordinates. Record chapter, original wording, and edition alongside important excerpts to relocate them across formats.

For research notes, set a rule such as “Read continuously in EPUB; verify citation pages in PDF.” Find a concept in EPUB, search the sentence in PDF, and record its printed page. The formats then complement each other rather than forcing one progress value onto every layout. Save important current notes before switching the primary format.

Duplicate files and formats not supported for reading

Importing the same file again may produce a Skip suggestion. Confirm the existing record works before accepting it. If you intended a revised edition but a similar title triggered duplicate detection, inspect content differences and import options. Skipping does not mean the new edition replaced the old one.

Book Isle's public scope for MOBI, AZW, AZW3, CBR, and DJVU is import, management, filtering, and synchronization. Appearance among available formats does not prove direct reading support. For reading, use an authorized original and an appropriate tool to convert to supported EPUB, PDF, or CBZ, then inspect conversion quality. Renaming an extension is not conversion.

Frequently asked questions

Why does merging not add another book to the shelf? Merging intentionally stores formats under one book record. Inspect available formats in details rather than shelf count alone. If separate edition records are needed, choose the appropriate new-book import option.

Why did same-named files not merge automatically? The same title is only a clue. Metadata differences, missing authors, or different editions affect detection. Do not arbitrarily change the author to trigger merging. Confirm the real relationship, then use available manual choices.

Does deleting a record remove only the primary format? Do not assume that. Deleting a book may also remove alternate files and reading records. Read the prompt and separately save important files and notes first. A merged record is not two independent backups.

Sources and version

Information checked on October 23, 2026. The public release is Book Isle 1.1.3, requiring iOS / iPadOS 15.6 or later. This guide is based on public feature descriptions and their entry points. Interface labels may change with the version. See Official App Store description and Apple release information.