You might consider the Harvard Open Metadata APIs, if they contain the works you are interested in. Free API and unlicensed content (the Amazon APIs do come with a license agreement/restrictions).
Doc here: https://wiki.harvard.edu/confluence/display/LibraryStaffDoc/LibraryCloud+Item+API
Example: https://api.lib.harvard.edu/v2/items?title=gates%20of%20fire&name=pressfield (which gets you an XML file with a lot of metadata including descriptions).
You can also search by ISBN.
If your works are in their DB, it's a great choice.