One day they will piss off one author or one major publisher and they will get sued out of existence. The argument that they assume that it is OK to reprint a copyrighted book unless the author complains will not hold up. I know that this is Google's stance, but that will not hold up either. It is really very easy to figure out if a book written in the 50's is public domain. The answer is that it IS NOT in public domain, unless the author specifically relinquished his copyright (which d.a. levy did and Brautigan did on at least one book, but very few authors do). I believe that in the US, it is 70 years from the author's death. Assuming that the author was alive in the 50's when the book was published, then it is impossible that it is in public domain.
Also, If the author is long dead, but the book is republished, the new publisher owns the copyright to the specific book, but not the title. They can add a foreword and then the book, as they printed it is their copyright, but you could always go back to an earlier edition and use that as your source and you would not be violating their copyright. I have heard that some publishers that specialize in reprint titles (like Dover books, who sells Poe, Twain, etc for $1 in horribly cheap paperbacks) may actually change or add a word, which then makes their printing copyrightable. Anyone copying that book with the added word would violate their copyright.
Bill
also, some authors die without a publisher, executor, or heirs to guard the copyright. This would mean that there would be no one with legal standing to sue you for publishing their work, but it would technically be illegal.
