For the first question: for matte I recommend Moab Entrada Fine Art, which is 2-sided and comes in both Natural (no brighteners) or Bright White (with brighteners) and both 190 and 300 gsm versions -- for a total of 4 combinations, all 2-sided. As usual, apply a brush over the surface before printing to minimize the chances of loose paper specks from coming off afterwards. The 190 weight is probably more appropriate for a book. 300 makes it thick and the pages a little harder to handle and turn, but then again it depends on how big you plan to make your book. Pretty economical.
Other options include Moab Kayenta (less expensive) and Red River Dourian Art (more expensive). Dourian should give you the deepest black of these three.
For non-matte I recommend Moab Kokopelli Studio Semi-Gloss 285, which I use in my own hand-made books. Not too glossy, good weight, good gamut, nice all around performer, and 2-sided of course. Of course this will have the deepest black and largest gamut of all the papers listed here.
Eric, are you creating signatures with more than a couple of folios?---I have samples of both those papers (Moab) and like them but would be afraid that they would present problems with signaures of more than a couple of folios--and handsewing also.