[msavazzi]

different approach:

# -*- coding: utf-8 -*-
__license__   = 'GPL v3'
__copyright__ = '2025 Massimo Savazzi'
__my_version__ = "1.0.0"  # Miscellany

"""
In order to manage Physical Books (.pbook) files, we define a Calibre plugin that treats .pbook files as ebooks.
It does import the info from the file and sets the metadata accordingly.
The .pbook file format is assumed to be a simple text file with key=value pairs, based on TOML e.g.:
[metadata]
title=Boook Title
author=Book Author
publisher=Book Publisher
ISBN=9788888888888
source=if scraped from a website, put the name here
publication_date=Book Publication Date
language=two-letter language code, e.g. it, en, fr
tag=Physical - all tags, comma-separated will be imported
"""

from calibre.customize import FileTypePlugin

class PBookEbookImporter(FileTypePlugin):
    name = "PBook Importer"
    description = "Import .pbook files reading the Metadata and updating it accordingly."
    supported_platforms = ['windows', 'osx', 'linux']
    version = (1, 0, 0)
    author = 'Massimo Savazzi'
    minimum_calibre_version = (6, 8, 0)

    file_types = set(['pbook'])
    ebook = True  # <-- This makes Calibre treat .pbook as a real ebook

    on_postimport = True

    def postimport(self, book_id, book_format, db):
        # Same metadata logic as before
        path = db.format_path(book_id, book_format.upper(), index_is_id=True)
        if not path:
            return

        meta = {}
        in_meta = False
        try:
            with open(path, 'r', encoding='utf-8') as f:
                lines = f.readlines()
        except Exception:
            with open(path, 'r', encoding='latin-1') as f:
                lines = f.readlines()

        for line in lines:
            line = line.strip()
            if line.lower() == '[metadata]':
                in_meta = True
                continue
            if in_meta and line.startswith('['):
                break
            if in_meta and '=' in line:
                k, v = line.split('=', 1)
                meta[k.strip().lower()] = v.strip()

        title = meta.get('title')
        authors = [a.strip() for a in meta.get('author', '').replace(';', ',').split(',') if a.strip()] or None
        publisher = meta.get('publisher')
        source = meta.get('source')
        tags = [t.strip() for t in meta.get('tag', '').split(',') if t.strip()] or None
        language = [meta.get('language')] if meta.get('language') else None
        identifiers = {}
        if meta.get('isbn'):
            identifiers['isbn'] = meta.get('isbn').replace('-', '').strip()

        # Apply metadata
        if authors: db.set_authors(book_id, authors, notify=True)
        if title: db.set_title(book_id, title, notify=True)
        if publisher: db.set_publisher(book_id, publisher, notify=True)
        if source: db.set_tags(book_id, [source], notify=True)  # optional: add source as tag
        if tags: db.set_tags(book_id, tags, notify=True)
        if language: db.set_languages(book_id, language, notify=True)
        if identifiers: db.set_identifiers(book_id, identifiers, notify=True)

The only issue is that title sort is not correct as is equal to title