[DNSB]

Possibly a side effect of the logic changes that needed to be made in the Kobo Books plugin? Looking at the log:

Spoiler:

Running identify query with parameters: 
{'title': 'Detective Kubu Investigates Boxed Set', 'authors': ['Michael Stanley'], 'identifiers': {'isbn': '9798201972158', 'kobo': 'detective-kubu-investigates-boxed-set'}, 'timeout': 30} 
Using plugins: Kobo Books (1, 9, 0) 
The log from individual plugins is below 

****************************** Kobo Books (1, 9, 0) ****************************** 
Found 1 results 
Downloading from Kobo Books took 1.888092279434204 


--- 
Title               : Detective Kubu Investigates Boxed Set
Author(s)           : Michael Stanley
Publisher           : ​White Sun Books
Tags                : Mystery & Suspense, International, Fiction & Literature, Short Stories
Series              : Detective Kubu #1
Languages           : English
Rating              : 
Published           : 2021-12-04T13:00:00+00:00
Identifiers         : kobo:detective-kubu-investigates-boxed-set, isbn:9798201972158
Comments            : b'<div class="synopsis-description" translate="no"><p>In this BOXED SET of all the Michael Stanley short stories included in the successful Detective Kubu Investigates 1 &amp; 2 and African Mysteries collections, there are thirteen twisty cases from Botswana and elsewhere. There\'s also an interview with Kubu himself, and exclusive excerpts from the new Kubu novel <em>A Deadly Covenant</em> to be released in 2022.</p>\n<p>A man is killed while rhino poaching, but is it as straightforward as it appears? A garbage collector makes a horrifying discovery in a bin. Is he the culprit or a victim? A witch doctor sets out to solve crimes with the help of the spirits. How does that work out? A man is stabbed outside a bar. Is it just a jealous fight or is there something much more sinister behind it? A writer at a weekend party is writing a noir short story set in the house where he\'s staying, but it seems to be coming true.</p>\n<p>In seven of the stories Kubu investigates murders in Botswana. Four detectives with very different styles and methods solve cases in South Africa, and there are two bonus stories set outside Africa.</p>\n<p>Best-selling British mystery author Peter James wrote of Michael Stanley\'s work, "I was gripped and entranced from the first page. A wonderful, original voice—McCall Smith with a dark edge and even darker underbelly."</p>\n<p>Michael Stanley is the pen name of two South Africans—Michael Sears and Stanley Trollip—who write fiction together. Their award-winning novels featuring Detective Kubu are <em>A Carrion Death</em>, <em>The Second Death of Goodluck Tinubu</em> (<em>A Deadly Trade</em>, outside North America), <em>Death of the Mantis</em>, <em>Deadly Harvest</em>, <em>A Death in the Family</em>, <em>Dying to Live</em>, and <em>Facets of Death</em>. They also have a stand-alone thriller <em>Shoot the Bastards</em> (<em>Dead of Night</em>, outside North America).</p>\n</div> \r\n    ' 
identify - title: "Detective Kubu Investigates Boxed Set" authors= "['Michael Stanley']"
KoboBooks url: 'https://www.kobo.com/ebook/detective-kubu-investigates-boxed-set'
parse_details - kobobooks_id: "detective-kubu-investigates-boxed-set" 
parse_details - title: "Detective Kubu Investigates Boxed Set" 
parse_authors - author: "Michael Stanley"
parse_authors - authors: "['Michael Stanley']"
parse_details - authors: "['Michael Stanley']" 
Script page_metadata= {'@context': 'http://schema.org', '@type': 'Product', 'name': 'Detective Kubu Investigates Boxed Set', 'description': 'Read "Detective Kubu Investigates Boxed Set Detective Kubu" by Michael Stanley available from Rakuten Kobo. In this BOXED SET of all the Michael Stanley short stories included in the successful Detective Kubu Investigates 1 & 2 ...', 'image': 'https://kbimages1-a.akamaihd.net/85342451-7a1d-4938-a051-0840f1d359f1/180/1000/False/detective-kubu-investigates-boxed-set.jpg', 'releasedate': '2021-12-04T05:00:00', 'sku': '9798201972158', 'gtin13': '9798201972158', 'offers': {'@type': 'Offer', 'price': 5.99, 'priceCurrency': 'CAD', 'availability': 'http://schema.org/InStock', 'url': 'https://www.kobo.com/ca/en/ebook/detective-kubu-investigates-boxed-set'}, 'brand': '\u200bWhite Sun Books'}
pubdate from JSON: 2021-12-04 05:00:00
parse_series - series_name: "Detective Kubu" 
parse_series - series_name_node: "b'<a href="/ca/en/search?query=Detective%20Kubu&amp;fcsearchfield=Series&amp;seriesId=ab40be00-56a0-53c8-9b6c-4c75b7c9354e" data-track-info="{}">Detective Kubu</a>    '" 
parse_series - series_index_node: "b'<span class="sequenced-name-prefix">series</span>\r\n\r\n    '" 
parse_series - series_index_node.text: "series" 
parse_series - series_index_text: "series" 
parse_series - Unable to get series number from series info
parse_series - series_name=Detective Kubu, series_index=None
parse_rating - rating: "0"
parse_language - language: "English" 

******************************************************************************** 
The identify phase took 2.07 seconds 
The longest time (1.888092) was taken by: Kobo Books 
Merging results from different sources 
We have 1 merged results, merging took: 0.00 seconds

Given that calibre wants a series index when there is a series present, I suspect it is being defaulted to 1.0 though I could be totally incorrect about that.