There is something not unlike grief that one feels at the end of a really good book. I recently finished re-reading (for about the 4th time) the entire Patrick O'Brian Aubrey/Maturin novels, and I always feel a profound sadness, this time in particular because O'Brian died since I last read them, before he could finish the 21st book, which might have brought the series to an intended conclusion. I am trying to read something similar that got favorable reviews (Captain Killburnie by William Mack) but it is a very poor simulacra.