They are nondestructive , cost effective and simple. It is possible to use a scanner with an automatic document feeder but that requires cutting up the book which is both destructive and requires help from a sighted person. This is non destructive and can be done independently if you have a little vision. Buying your own scanner and the right software for your computer is somewhat expensive even more so if you don’t have a computer. This is free. This is also simple while learning the tools on the computer can take considerable time. The only major thing I wish it would do is let me add semantic markup so the book can be navigated easily and complex tables can be read correctly . That said the book eye is a great start to making any book accessible. If I want to do more I can always import into acrobat and in many cases just using the book eye will be good enough.
When using the book eye I recommend using the high quality image setting but if you find it too slow you can get a good enough result on normal quality. You should output a searchable PDF. This is equivalent to asking for OCR and you will not be able to read your book without it. You should change to 300 DPI to improve recognition quality and rename the file to something meaningful so you can find it later. You can save it in a variety of ways but I recommend cloud storage or email with cloud storage being my preference since it improves find ability and cross platform access.