Paul has a Google Pixel 4a that he's using to scan books. It works fine, but with larger books, the image is distorted. How can he fix that? He was thinking of using an external wide-angle lens to attach to it. Leo says that those third-party lenses will distort the image even more. Especially if they're cheaper lenses, Paul could break up the page into multiple images.
Chris Marquardt says that there are apps that will take out the distortion. The Google Drive app has a document scanner built in that straightens out the distortion and even does OCR. Google also has a dedicated app called PhotoSpace Scan. Using an app to correct for the distortion would be better than trying to compensate optically. A flatbed scanner that's designed to scan books is also a good idea.
Doctor Mom says to check out OpenLibrary.org. They have books that are already prescanned. Google may have also scanned it. She also recommends the CZUR Document scanner. It has a camera mounted from above, dedicated lights, OCR, and image distortion, all in the scanner. It's a great-looking device.