if you're interested in paperbacks or audiobooks you could check out book lender (formally booksfree) it's like netflix for books as in you have a list & they send you whatever number you singed up for and when you send them back you get more. you can keep them as long as you want & depending on if you have the unlimited plan you can read as many as possible during the month.
they have various plans for paperbacks and/or CD & MP3-CD Audiobooks and i think they have kid's books too. they usually have a half-off the first month thing going on, so you can check it out if you want.

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