Checking e-books

Ebooks are often written in some text processor, and converted to ebook later. I checked a collection of ebooks (not scanned ones…) and discovered a large amount of simple errors.

Would having an ebook (or document) checker as a paid service be worthwhile?

Can any of these errors be ascribed to encoding-limitations?
(EG: Some errors can be triggered by having hard returns (the standard translation of a raw ASCII return) where soft returns are required)

No, it is just spelling errors and unnecessary or missing spaces etc. I converted all XML first.