A 1 year subscription to Kindle Unlimited is $119.98, which works out to be just over $10 per month.

Source: https://www.devicemag.com/how-do-i-get-kindle-unlimited-on-my-iphone/

Kindle Unlimited: 3 months for £7.99 (save 50%) -

Source: https://www.thesun.co.uk/shopping/12798464/amazon-black-friday-sales-deals/

Kindle Unlimited is the only reading-centric subscription service that Amazon offers, but it's not the only Amazon subscription that allows for eBook downloads.

Source: https://www.slashgear.com/1346455/how-to-cancel-kindle-unlimited-subscription-guide/

Kobo Plus is an all-you-can-read rival to Kindle Unlimited.

Source: https://www.cnet.com/tech/services-and-software/kobo-takes-on-kindle-unlimited-with-new-all-you-can-read-ebook-subscription/

Plus, with Kindle Unlimited, you never have to worry abot late fees or overdue items.

Source: https://www.devicemag.com/how-do-i-get-kindle-unlimited-on-my-iphone/

There is also the option to delete or share a highlight from this window or view popular highlights if the book was obtained via Kindle Unlimited or bought directly from Amazon.

Source: https://screenrant.com/how-to-highlight-text-on-a-kindle-and-find-it-later/