The best textbook on C I have is C: A Software Engineering Approach by Peter A. Darnell and Philip E. Margolis. While it is (undeservedly) not as famous as other books, I found it very readable and it handles all the details K&R skips over.
It has two disadvantages though:
- It is from 1996, so it does not cover C99. (This should be fine with you since you are interested in C89.)
- It is quite expensive.
Edit:
Another book of interest is C Programming FAQs by Steve Summit. While I don't have this book in print, the accompanying web site helped me a lot in understanding the less obvious features of C.