This is part of my attempt to educate myself about the Hugo nominees for Best Related Book, though really it will be a travesty if the Cambridge Companion to Science Fiction doesn't win.
The Best of Xero is a compilation of articles and letters from the US science fiction fanzine Xero, which ran from 1960 to 1962. None of this is of huge literary merit. There are some bits that I did find very interesting - the articles by James Blish on Kingsley Amis' New Maps of Hell, and by Donald Westlake on getting sf stories published, and the ensuing slew of correspondence. There were several long articles on comics I will never read which I skipped. There are a couple of really bad articles - the one on Clark Ashton Smith is a nadir, and I was unimpressed by Lin Carter's book reviews.
So I'm sure this book will appeal to those fans who were around at the time (surely not a huge number) and to those who are interested in the history of the genre (including me). But I wouldn't put it top of my list, at least not with fjm in competition.