I’ve never had that problem but if it was me, I’d be trying to get the tracks into the right order using Windows Media Player.
If you’re only going to listen to it once, you could try deleting tracks 10 to 18 on the Fuze, listen to the first half, then reload the book when you’re ready for the second half - which might, or might not work.
Have you looked around the board for a solution?
eg
http://forums.sandisk.com/t5/Sansa-Fuze/Audio-Books-sorted-by-Title/m-p/231046#M2663
and
http://forums.sandisk.com/t5/Sansa-Fuze/AUDIO-BOOKS-ON-SANSA-FUZE/m-p/214944#M954
