A brief preamble: please to note that these posts are about how I do PW stuff. Other editors may work very differently.
A starred review from PW is a big deal. Like diamonds, their value is in their scarcity. Also like diamonds, that scarcity is to some extent artificial. The question of how many books to star is necessarily going to have a rather vague and arbitrary answer: few enough that a star really means something, while making sure that really outstanding books get the recognition they deserve.
As far as I'm concerned, a star means "This is better than others of its kind". It's useless without context. I might give a star to a decent book that's head and shoulders above others of its subgenre. I might withhold one from a consistently superb author who's kind of coasting on their superbness. These evaluations change all the time as the genre changes. Last year we got in a whole bunch of "year's best" anthologies at once, and I think four out of five were starred. That tells me that the bar should be raised. When the next round comes through, I'll be starring those that don't just stand out from the crowd of anthologies--because just about all of them will do that simply by virtue of being the year's best--but that stand out from the crowd of YBs. Otherwise the value of the star is diluted.
I can't read every book that we review, so I rely on reviewers to recommend stars. It's important to remember that reviewers are in this business because they love books, and they especially love good books. I'm with them on that, personally. When I saw Ratatouille (a gloriously entertaining movie, which anyone interested in reviewing should watch), I frowned slightly at the statement that negative reviews are more fun to write and read than positive reviews. I've always enjoyed writing positive reviews much more. When I was reviewing for PW, I took particular delight in rewarding good books with highly quotable reviews, and later in seeing those reviews excerpted on author websites and book jackets. The highest reward a PW reviewer can give is a recommendation for a starred review. My job now, as reviews editor, is to decide whether to go with those recommendations.
I keep an eye out for reviewers who love to gush. For some people, a book is either wretched or exalted, with nothing in between, and since I take care to match books with reviewers who are likely to appreciate their nuances, that may lead to a lot of exaltedness. When I get star recs from those reviewers, I hold my judgment until I've edited the review and looked through the book.
Some reviewers will suggest a star as an "A for effort" sort of thing, which I really prefer not to do. The truth of that suggestion will usually reveal itself in the review or the accompanying notes from the reviewer, which will reluctantly admit that perhaps the book is flawed in some significant way. Even if the author was trying very hard, even if it's a substantial improvement over their past work, significantly flawed books don't get stars in my section.
There are also reviewers who are bitter old cynics. I take their star recs very seriously, because they're stingy. If they start seeming too stingy, I'll ask whether I've been sending them the right books; if someone hates epic fantasy and I've been sending nothing but, those books probably aren't getting a fair shake. The flip side of that is keeping an eye out for reviewers who are super huge fans of a particular author and request all their books. I usually agree to requests, because it's great to have a review from someone who knows all the author's work and can give a detailed critique of the new book in context, but it's one thing to appreciate someone's work and another thing to recommend a star for everything they write. If necessary, I'll start sending that author's books to a different reviewer to ensure that they get an honest look without any rose-colored glasses in the way.
Finally, I look at each section and the ones planned for the next month, and I space the stars out so that we don't have three one week and none the next week. In general, each section has between five and eight books (usually closer to eight than five), and one or two of those will be starred. I'd say I star around 15% or 20% of reviews. That seems a little high to me, though maybe it's not if you consider that a book generally has to be at least halfway decent for us to review it in the first place. Still, I should probably keep it closer to 15%. Maybe I am a soft touch after all.
