Many thanks for the advice Turtle91, and Toxaris. I took your points about OCR. I have OCR'd them as well, so can change formats as needed.
Interesting that 400dpi reduced errors a lot.
I've noticed the option i use:
Best Mode - Color & Grayscale 300 dpi, B&W 600 dpi
since I've been scanning in B&W it must have got 600 dpi!
I guess the option below is not really likely to be needed for reading novels:
Excellent Mode - Color & Grayscale 600 dpi, Monochrome 1200 dpi