I've actually done quite a bit of extensive study on this area (my book maps thread) and Torstan has great advice to give. If I may be so bold as to add some advice to this effect? ...

I prefer to know the exact dimensions of the book and where you bleed marks are going to be. Unfortunately, the printing and publishing industry doesn't really have a set book dimension, take a look at a bookstore shelf some day and just notice all of the different sized books out there. Unless you are publishing under some major name, the book might not be your standard paperback size. If you create a map or piece of artwork at one dimension, and it has to be printed to fit into another sized area, it could skew the effects. (I found this out with my Phenomedom Map.)

Less IS MORE. I like to make the map at least twice or three times the size of the original print. Once the work is done, condense it the size it needs to be printed at. Don't try to add too much detail into something, because once it gets resized, it might become meshed and mired and looking like a blob. When saving to a PNG or JPG to look at it, save it at the size it will be printed so you can get a look at the final piece.

Gameprinter might have some more useful information or more correct information, but most printers have a definite distinction between Greyscale and Line Art. Line art must be made only from lines and usually must be sharp and crisp with no screens, grays or middle tones. They usually need to be saved around 600 dpi. Greyscale usually is accepted at 300dpi, but different printers have different requirements when it comes to printing interior artwork and greyscale.... from what I've gathered, most of the time it has to be Line Art.

Depending on who is actually putting the book together for print, also determines how you should treat Text. All text should probably be left seperate and off the map (keep your layers all seperate for text) DONT compress the whole thing and save over it cause (as mentioned before) Different printers have different requirements on how they handle typesetting, tho now adays it is probably safe to assume that if you embed the text into the file, they can handle it.... this is just a safety net ....

I do know that printers usually love PDF's ... and where everything is already set up for them to print (using their guidlines of course) .... so keep that in mind

Ok... I'm done blabbing have fun!