Powell's Books provides an API (http://api.powells.com/stable) and direct links to their book covers by ISBN13 only.
Regarding the limit on daily use of the Google Books API, I think from when I used it before that if you access cover links through the Dynamic Links API (https://developers.google.com/books/docs/dynamic-links) there is no daily limit.
> Date: Tue, 5 Nov 2013 15:13:35 +0000
> From: [log in to unmask]
> Subject: [CODE4LIB] display book covers
> To: [log in to unmask]
> Hi all,
> Anyone have some good resources about tools for gathering book cover images? I'm building that into our next catalog update, which uses Blacklight, but I'm not necessarily looking for Rails-only approaches. My questions are more general:
> What sources are out there? (ex. Google Books, amazon)
> Making it work?
> I'm trying out Google Books at the moment, just making a call to their API. This can be asynchronously and loaded after the rest of the page, or cached, perhaps even store the url in solr or a database table?
> I am trying out a Google Books gem, which is just a wrapper for the api.
> Other thoughts?
> Thanks in advance,
> Adam Wead
> Systems and Digital Collections Librarian
> Library + Archives
> Rock and Roll Hall of Fame and Museum
> [log in to unmask]
>  https://github.com/zeantsoi/GoogleBooks
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