Look up "Easy Reader" by Dolphin computer access. It's for Windows, IOS, and Android, and it integrates with many libraries for people with print disabilities in various countries.
That will have the added benefit of giving you a list of those resources to sign up for as well...
The only things missing from Easy Reader are "NFB newsline" for magazines and newspapers and "NLS Bard" for accessing tons of books, but those are both only in the US so may not matter to you.
If you are in the US though, than get signed up with those, because they are really valuable even if they use separate apps.
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Now all of those are services specifically for people with print disabilities, but your local library (or at least a bigger one near by) will also have their own ways for accessing ebooks.
Check out this article to learn more about the various services that your library might be offering, and how accessible they are.
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And, if your trying to scan existing books and you have an IPhone or IPAD, I'd suggest either Seeing AI as others have mentioned, or "Voice Dream Scanner" which is another good app and may be better for what your doing.
Just make sure you have decent lighting, and hold the camera a few inches away from the page while letting it do all the focusing for you, only making small adjustments as needed. If you can, look into getting a boom arm with grip, or a stand for putting your phone/tablet on with a hole for the camera. That will make your job much easier.
A higher quality alternative may be to buy a good flatbed scanner, and a copy of fine reader 14, for Windows/Mac which will be more convenient for multiple pages.