I've only skimmed through it, the most recent time in trying to find some evidence for some argument on Z, IIRC. It's not the clearest book, IMHO. The Quran Explorer is a good resource - it has 3 slightly different English "interpretations".

http://www.quranexplorer.com/quran/

These letters are one of the miracles of the Qur'ân and none but Allâh (Alone) knows their meanings.

Yup. :-/

Cheers,
Scott.