He died when the Serenity returned to it's little colony planet and found it in ruins, remember? It was right before they went through Reaper Space.
Wish I could ban certain people from posting in certain topics.
Anyway, I can't imagine how they'd manage w/o Book and Wash...
Come now, just because they're filthy and illiterate should be no reason to discriminate against them. Some of history's greatest people managed quite well without either a book or a wash. Think of Genghis Khan for one.
/me has SMIT'D Rictor for the above pun
If you look in the Outtakes section of the Serenity DVD, you'll notice that Nathan Fillion (Mal) orders Book tied front and center because "he's our friend, it's an honor". He also tells Kaylee to tie a little "hood ornament" to the ship. :D