I have lived in the GCC for 15+ years. The only confiscation I know of personally was a recording of the ladies figure skating in the Olympics in the late 90s.

If your books are for personal use and have no pornographic pictures, you're OK. I have had books on Buddhism etc. sent to me via Amazon. No issues. If needed, you can buy books on astrology here in some book shops (very popular in some Asian communities) but books are expensive here