Which color space (sRGB or ProPhoto) should I use in LR4 BETA in order to produce a book in the Book Module?
Thanks. You mean that I should use the sRGB color space in the LR4 BETA prefences, then work the images in the Develop module, then edit my book in the Book Module and send it to Blurb for printing. If I follow that workflow I should get a close call to what I see in my monitor?
Thanks. You mean that I should use the sRGB color space in the LR4 BETA prefences
No you should not touch that and just leave it at default. It has nothing to do with the color space that Lightroom uses which is always prophotoRGB with linear gamma, no matter what you select in that preference. That preference is for determining what space is used in external editors (think Photoshop). In the book module, Lightroom always sends the images to blurb in sRGB format, no matter what your source color space for your images was. It simply always does the right thing. No need to worry.
You can only work (process) images using the internal color space which is close to ProPhoto RGB. When a book is uploaded to Blurb, it is converted to sRGB. But Blurb uses a CMYK Indigo digital press and LR can’t soft proof CMYK so soft proofing to sRGB is pointless.