I have just bought a digital technical book for my son, which was to be used on his Kindle. Unfortunately, due to the file format of the book (.acsm), this cannot be done. I have downloaded Adobe Digital Editions, and found there is, unbelievably, no text to speech facility as there is on his Kindle. My son is severely Dyslexic and this facility is a must. For anybody who might not understand what this means for him, I can tell you that if you can read a page of text in ,say, 3 minutes, it would take him 15 minutes. Please Adobe can you upgrade Digital Editions to enable Text to Speech?
I am having the same problem. At this point, from what I am reading, you will need to get the book from the publisher in accessible format. Since your son has a diagnosis he is entitled to have an accessible version of the text provided, usually in PDF format which can be "read out loud" (under View tab) in Adobe Reader. You can adjust the voice and speed. From my experience getting college textbooks, you are required to purchase the book then they provide an accessible version. Also, you may be able to get accessible book formats through the National Library Service. Google: books for the blind.