from what I see on book's amazon page (
http://www.amazon.com/Treasure-High-...dle+Edition%5D)
This book has amazon drm applied. (one of easy ways to check is look for 'Simultaneous Device Usage: Unlimited' on book's page)
This mean for this book regular conversion won't work because either Amazon doesn't want you to do so.
Somebody told me that Apprentice Alf is your friend in such situations (search right here on MobileRead)