The one I use is Luzme It queries several stores including Kobo, Amazon, B&N and in several countries.
It then for each book shows the price that it last saw for each source and country.
It is searchable by book name and author and series, although the series data is not complete as it comes from the stores.
You can set up a wishlist of books and ...
Calibre is a downloadable (free, donations accepted) application that will allow you to search over multiple stores, for content. Using the get books function, to provide information like comparative pricing between retailers and DRM status of the work at different retailers.
Yes there are. The one I remember is Inkmesh.
You can filter by price, type (ebook, magazine, audiobook, etc.) device and language. Its database has large gaps though.
This site does not provide DRM status.
The internet archive https://archive.org/ lists both works they host as well as works in other libraries. While most (all?) of the ebook are available without cost the majority are public domain works, there are also many Create Commons & fair-use works. There is not a good way to search for only PD works, but due to the type of results returned that ...
If you're looking specifically for public domain/open licensed works rather than simply works that are available for free, you can always use Google's Advanced Search options to find works that are filtered by usage rights--you can select:
Free to use or share
Free to use or share, even commercially
Free to use, share, or modify
Free to use, share, or ...
Amazon only enhanced search engines (I'll group these together since they don't quite fit the question, but are still worth a mention).
Jungle-Search is an interesting search engine. It's not limited to ebooks and is Amazon only (though you can choose from various Amazon stores, such as CAN/US/UK/GER/FRA). The purpose of this search engine is to allow you ...
There is a decent search engine called Leatherbound ebook search engine. Like Inkmesh and Luzme it allows you to search for a book across multiple stores and price compare. Here is a sample search result (for an entertaining book I might add).
In addition, you can search for printed books, free ebooks, ebook under $5 and some advanced search options.
There is the following website called JustFreeBooks. It has public domain texts, open books, free audio books and ad-supported books. When searching for a specific title for exemple The Iliad by Homer, a list will appear with links to different websites that have this classic book.
Apart from Internet Archive mentioned by Mr. Jenkins: https://archive.org/
You could try Project Gutenburg, which has a search bar on the top left hand corner:
Their site says:
Project Gutenberg offers over 42,000 free ebooks: choose among free epub books, free kindle books, download them or read them online.
We carry ...
I think the best approach is to find audiobook sharing websites that have an advanced feature for narrowing the search result to "narrated by Author". Seems like simplyaudiobook provide this feature
Also you can simply search in google "audio book narrated by author" and find many personalized lists such as: