playing audio books downloaded from Nat Library for the Blind on Alexa or some other speaker?

I have a friend who is blind and crippled. She got in touch with NLS The National Library for the Blind and Physically Handicapped. They sent her a reader but they only send one audio book cartridge at a time. We can download audiobooks for her but she cannot see to operate an iPad or iphone. Is there some way to play these on a speaker that answers to voice commands? She has an Alexa but it only plays books bought on Audible, right? This lady is a voracious reader and needs to be able to read the downloaded books as she has nothing else to do. Please help me think of a way she can hear her books with commands. Thank you in advance for any help you can give me.