I want to find out whether these sentences are grammatically incorrect:
It is more better than your book
It is far more better than your book
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Neither are correct. "better" is a comparative form of "good", so you do not need to (and should not) say "more better": say either:
It is better than your book.
It is far better than your book.
If you study the grammar point comparison forms of adjectives you will find that
1 certain adjectives have the endings -er/est
2 others use more/most before the adjective
3 some have irregular forms, e.g. good better best
Using "more better" is against normal grammar, and if it is used it is uneducated and substandard.