@JessMahler
Bookshop.org is great, believe their sales support indie bookstores. Definitely works for at least US and UK.
Waterstones and Blackwell's are decent for UK, Blackwells for SURE ship internationally, Waterstones might

On top of the library point, most libraries probably have an ebook/audiobook library you can access for free. Libby and Overdrive are most common. This goes for both US and UK.