An author friend mentioned https://www.bundlerabbit.com/ to me.
Basically it’s a site where an author can upload his or her book and ‘curators’ can bundle books together to sell as a package. Each author gets a share of 70% royalty and the reader gets five, ten or so books to read for a bargain price.
So if the individual book is 1.99 and there are 5 at that price that’s 9.95 but the bundle might be on sale for, say, 7.50. The authors get 5.25 split between them. That may be a sale they wouldn’t have got for the stand alone.
Currently I’m only putting short books in – to see how it goes. It’s a wee bit fiddly, and obviously one has to register and have a paypal account (for royalties).
Readers can look at bundles they want – and either pay what they want or the set price – then the books are downloaded to their Kindle. They can opt to donate some of the price to charity
Copyright stays with the individual authors and they can be sold elsewhere. (Unless you’re in KDP Select – but that’s another case.