The whole text is on the WEB but the authors hope that most potential customers will just dip into the electronic version before buying a printed copy. Even CCTV systems that enlarge text may infringe copyright, but at least the copy is ephemeral, however systems for print disabled people usually produce reusable copies. Where individual users are making partial copies for their own use this is unlikely to be a problem. For now you need to be experts on Copyright and what can and can't be done legally under CLA rules. Abridged book-tapes are virtually impossible to use like this as the dyslexic reader will have great difficulty finding their place in the printed text.
Many libraries now sell a range of books and other products.
Item that may be of interest to dyslexic users are Pens, pencils, Post-it. Remember, only your customers can tell you what works for them.