I'm having the same issue. In my case I need just hardcover and kindle version of a book.
GetVariations (successor of AlternateVersions) is for some reason not working for books and just returns no result back.
The only possible way that I'm aware of is to do two API request (SearchItems) including the specific search index Books for books and KindleStore for kindle files. Not specifying the search index normally returns you just the hardcopy of the Books search index.
To differentiate between books and kindle version check the ItemInfo.Classifications.ProductGroup.DisplayValue or ItemInfo.Classifications.Binding.DisplayValue
For some unknown reason (at least to me) the API is returning only a subset of results when not specifying the search index (in the below example the kindle one)
Example
In the following example I looking for the hardcopy or kindle of the book with ISBN 9780262043649 by doing a SearchItem request.
a) Hardcopy with given search index
Payload
{
"Keywords": "9780262043649",
"Resources": [
"ItemInfo.Classifications",
"ItemInfo.Title"
],
"SearchIndex": "Books",
"PartnerTag": "*******",
"PartnerType": "Associates",
"Marketplace": "www.amazon.com",
"Operation": "SearchItems"
}
Response
{
"SearchResult": {
"Items": [
{
"ASIN": "0262043645",
"DetailPageURL": "https://www.amazon.com/dp/0262043645?tag=getabstractcom&linkCode=osi&th=1&psc=1",
"ItemInfo": {
"Classifications": {
"Binding": {
"DisplayValue": "Hardcover",
"Label": "Binding",
"Locale": "en_US"
},
"ProductGroup": {
"DisplayValue": "Book",
"Label": "ProductGroup",
"Locale": "en_US"
}
},
"Title": {
"DisplayValue": "Novacene: The Coming Age of Hyperintelligence (The MIT Press)",
"Label": "Title",
"Locale": "en_US"
}
}
}
],
"SearchURL": "https://www.amazon.com/s?k=9780262043649&i=stripbooks&rh=p_n_availability%3A-1&tag=getabstractcom&linkCode=osi",
"TotalResultCount": 1
}
}
b) Kindle with given search index
Payload
{
"Keywords": "9780262043649",
"Resources": [
"ItemInfo.Classifications",
"ItemInfo.Title"
],
"SearchIndex": "KindleStore",
"PartnerTag": "******",
"PartnerType": "Associates",
"Marketplace": "www.amazon.com",
"Operation": "SearchItems"
}
Response
{
"SearchResult": {
"Items": [
{
"ASIN": "B08BT4MM18",
"DetailPageURL": "https://www.amazon.com/dp/B08BT4MM18?tag=getabstractcom&linkCode=osi&th=1&psc=1",
"ItemInfo": {
"Classifications": {
"Binding": {
"DisplayValue": "Kindle Edition",
"Label": "Binding",
"Locale": "en_US"
},
"ProductGroup": {
"DisplayValue": "Digital Ebook Purchas",
"Label": "ProductGroup",
"Locale": "en_US"
}
},
"Title": {
"DisplayValue": "Novacene: The Coming Age of Hyperintelligence",
"Label": "Title",
"Locale": "en_US"
}
}
}
],
"SearchURL": "https://www.amazon.com/s?k=9780262043649&i=digital-text&rh=p_n_availability%3A-1&tag=getabstractcom&linkCode=osi",
"TotalResultCount": 1
}
}
c) No specific search index
Payload
{
"Keywords": "9780262043649",
"Resources": [
"ItemInfo.Classifications",
"ItemInfo.Title"
],
"PartnerTag": "*******",
"PartnerType": "Associates",
"Marketplace": "www.amazon.com",
"Operation": "SearchItems"
}
Response
{
"SearchResult": {
"Items": [
{
"ASIN": "B08BT4MM18",
"DetailPageURL": "https://www.amazon.com/dp/B08BT4MM18?tag=getabstractcom&linkCode=osi&th=1&psc=1",
"ItemInfo": {
"Classifications": {
"Binding": {
"DisplayValue": "Kindle Edition",
"Label": "Binding",
"Locale": "en_US"
},
"ProductGroup": {
"DisplayValue": "Digital Ebook Purchas",
"Label": "ProductGroup",
"Locale": "en_US"
}
},
"Title": {
"DisplayValue": "Novacene: The Coming Age of Hyperintelligence",
"Label": "Title",
"Locale": "en_US"
}
}
}
],
"SearchURL": "https://www.amazon.com/s?k=9780262043649&rh=p_n_availability%3A-1&tag=getabstractcom&linkCode=osi",
"TotalResultCount": 1
}
}
You can try those examples in the API's scratchpad.
More information about the search index of the product advertising API is available on the official documentation here