There is probably a lot more room for improvement. Anyone wanting the sample before buying may be quickly turned off. It's a 60MB zip file because the audio is bundled in. This easily deters anyone on their iPhone/iPad.
I've just added an interim step that allows people to download the PDF and audio files separately (and I've added the size of each file to the page).
(I bought the book anyway - you should probably give Daniel a kickback, actually.)