All four of the other volumes are worth reading. I'm putting 'Feed' in fourth place, because I disliked the setting and I exceedingly disliked Grant doing one particular thing (and I can't even begin to discuss what she did without extreme spoilers). However, although it was at least 100 pages before I got over that initial dislike, the story did affect me emotionally and I will probably go buy the second book at some stage.
In third place goes Jemisin's 100,000 Kingdoms, which I enjoyed but found slightly less memorable than the rest.
Second place goes to Bujold's Cryoburn which is yet another Miles Vorkosigan story. However, it does posit interesting questions as to what would actually happen if cryogenic freezing of people became widespread. It does suffer slightly from the 'the whole world is the same' effect of the examined world, but it's allowable for all that. This takes place on a different planet because it needs that separation for it to work politically.
And first place goes to McDonald's The Dervish House, in which he takes on near-future Istanbul and brings a city to life so well that I now want to go there. It rightly received the BSFA award, and I'd consider it a worthy Hugo winner too. Oddly enough, I suspect that if it gets beaten, it'd be by Feed.
(And just how, please, did Mira Grant/Seanan McGuire get last year's Campbell for Best New Writer, yet already have 6 novels in print, and another 2 already ISBNed?)