Hi LiJ I agree that 1 is OK, and 1 would be a very common usage. Sentence 2 is wrong and also doesn't make any sense. I don't like 3 and also don't think the grammar is appropriate.
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YankeeHi LiJGot it! Thanks, Amy.
I agree that 1 is OK, and 1 would be a very common usage.
Sentence 2 is wrong and also doesn't make any sense.
I don't like 3 and also don't think the grammar is appropriate. Maybe this instead:
This book was so difficult as to be completely incomprehensible/unreadable.