[miyoyo]

New reply, to separate answers

I'll post random info I find here

Book Metadata regex:

({"(?:.{8}-.{4}-.{4}-.{4}-.{12}|Book)":)?\[?{"(?:Recommendation":{"Reasons":\[\]},")?Contributors":"([^"]*)?","WorkId":"(.{8}-.{4}-.{4}-.{4}-.{12})","(?:Subtitle":"([^"]*)?",")?(?:SeriesNumber":"(\d*)","SeriesName":"([^"]*)?","SeriesId":"(.{8}-.{4}-.{4}-.{4}-.{12})","SeriesNumberFloat":(\d*),")?(?:Subtitle":"([^"]*)?",")?IsFree":((?:fals|tru)e),"ISBN":"(\d*?)","PublicationDate":"(\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}.\d{7}Z?)","ContributorRoles":\[.*?\],"(?:IsInternetArchive":((?:fals|tru)e),")?CrossRevisionId":"(.{8}-.{4}-.{4}-.{4}-.{12})","Title":"([^"]*)?","Description":".*?","Language":"(..)","ImageId":"(.{8}-.{4}-.{4}-.{4}-.{12})","PublisherName":"([^"]*)?","Rating":([0-9]*\.[0-9]+|[0-9]+),"TotalRating":(\d*?),"(?:RatingHistogram":({"1":\d*?,"2":\d*?,"3":\d*?,"4":\d*?,"5":\d*?}),")?Slug":"([^"]*)?","IsContentSharingEnabled":((?:fals|tru)e),"RedirectPreviewUrls":\[(?:{"DrmType":"([^"]*)?","Format":"([^"]*)?","Url":"([^"]*)?","Platform":"([^"]*)?","Size":(\d*?)},?)*\],"HasPreview":((?:fals|tru)e),"Price":{"Currency":"(...)","Price":(\d*?(?:\.\d*?)?)},"(?:PromoCodeAllowed":((?:fals|tru)e),")?EligibleForKoboLoveDiscount":((?:fals|tru)e),"IsPreOrder":((?:fals|tru)e),"(?:RelatedGroupId":"(.{8}-.{4}-.{4}-.{4}-.{12})",")?Id":"(.{8}-.{4}-.{4}-.{4}-.{12})"}

Kobo image distribution:

https://kbimages1-a.akamaihd.net/{IMAGE-UUID}/167/256/100/false/image.jpg
                                             /     |   \      \
                                     Horizontal    |    \     Monochrome
                                                   |  JPEG quality
                                                Vertical

As far as I can tell there are no restrictions to the image resizing, except that it has to keep the aspect ratio.