Colour Space:

Adobe RGB or
ECI RGB (profile link)
8 or  16 bit

File Format:

TIFF (LZW is ok)
JPEG (lowest compression, highest quality)

File Size:

The book format is approx  50 x 70 cm
(19,68 x 27,55 in), so a picture
on a spread (landscape format) would be approx
100 x 70 cm (39,36 x 27,55 in) max.
A single page picture around  50 x 70 cm.

Resolution:

We are printing fine screening of 80 lines.
Therefore resolution is  406,4 DPI (89,6 MPX).
We know that these technical requirements are not
easy to meet. Please note that this is the top limit.
Basic Limit for the resolution is  24 MPX.