Being an editor at heart, poor usage decreases the enjoyment I derive from certain books.
I heartily approve of self-publishing as it brings us many wonderful books that would otherwise never be offered to the public. Publishing companies no longer determine what we will or will not read.
In this age of self-publishing, however, too many people publish poorly edited books. Please, please, do yourself and your readers a favor and get someone who knows the language to read and edit. An author is usually too close to the work to see obvious mistakes, as they see what is intended rather than what is actually there. Even “just a friend” can help you find usage mistakes, but one of your former teachers or other knowledgeable person would be better. I’m sure almost anyone can find a beta reader or two to make suggestions and corrections.
Lacking those resources, set your work aside for a couple of weeks and then read it, not with love in your eyes, but critically. This is difficult. After all the effort and time spent in creating it, you won’t want to be critical of your baby. But a couple of re-reads and the resulting corrections will end in a project you can be proud to publish.
Edit, revise, rewrite, repeat before publishing.