My middle son recommended this book and went so far as to lend me his copy. While I was reading it I saw a Thing online that purported to list the top 75 SF books ever written. I didn't much agree with the list, but The Mountain in the Sea was in it, round about number 30 as I remember.
   Well, both son and list were spot on. This is a splendid book, full of thought-provoking ideas, fascinating world building, and nicely crafted, conflicted characters. Not to mention a fairly dense plot.
   What more could you ask for?
   I thoroughly recommend The Mountain in the Sea, although I did spot one minor error that the editor really ought to have picked up. I won't put it here, but if you want to find out what it was, venture over to my professional site and click on the errata tab.