Book Printing - Halftone or Contone?

[JimD]

I've recently become aware of an on-line book printing service, SharedInk.
They are reviewed in this article:
http://www.naturephotographers.net/articles0405/mh0405-1.html

SharedInk uses a HP/Indigo Ultrastream 3000 digital offset press.

'The Ultrastream 3000 prints at a resolution of 800 x 800 dpi,
with an effective line screen of 150-180 lines per inch. '

When output sharpening for this process should I use the Halftone or
Contone output sharpener?

Since I can get selected proof pages printed for a nominal fee I'll be able to
confirm my choice. I know so little about printing on anything other than an
inkjet I'd appreciate guidance from the gurus.

Thanks,
JimD

[Bruce Fraser]

I'd send 300-ppi files, and try Halftone 150 (Coated or uncoated) 300 ppi and Contone 300. I suspect the halftone sharpener will work better