Behind every book review there are two key figures:
a book review editor and a reviewer. Editors decide
whether a book is reviewed in their publication, when
the review appears, how long it is, and who writes the review.
  When many periodicals feature the same books,
this does not prove that the editors of different
periodicals have not made individual decisions.
Before publication, editors receive news releases and
printer's proofs of certain books, signifying that the
publishers will make special efforts to promote these
books. They will be heavily advertised and probably
be among the books that most bookstores order in
quantity. Not having such books reviewed might give
the impression that the editor was caught napping,
whereas too many reviews of books that readers will
have trouble finding in stores would be inappropriate.
Editors can risk having a few of the less popular
titles reviewed, but they must consider what will be
newsworthy, advertised, and written about elsewhere.
  If these were the only factors influencing editors,
few books that stand little chance of selling well would
ever be reviewed. But editors feel some concern
about what might endure, and therefore listen to
literary experts. A generation ago, a newspaper used
a brilliant system of choosing which books to feature.
The book review editor sent out a greater number of
books than reviews he actually intended to publish.
If a review was unenthusiastic, he reasoned that the
book was not important enough to be discussed
immediately, and if good reviews of enough other
books came in, the unenthusiastic review might never
be printed. The unenthusiastic reviewers were paid
promptly anyway, but they learned that if they wanted
their material to be printed, it was advisable to be
kind.
  Most editors print favorable and unfavorable
reviews; however, the content of the review may be
influenced by the editor. Some editors would actually
feel that they had failed in their responsibility if they
gave books by authors they admired to hostile critics
or books by authors they disapproved of to critics
who might favor them. Editors usually can predict who
would review a book enthusiastically and who would
tear it to shreds.