A very interesting thread, which brings up some interesting issues. My answer to the question in the original post? It may not be legal to copy that book. Still, *if* the original copyright holders have no interest in it, then it is not only ethically acceptable, but necessary, that someone preserve it. Let me explain:
One issue that I have not seen mentioned is the issue of copyright term duration, which large companies labour to extend to the detriment of a lot of other works. I defend the right of any creator to benefit from their works, but the general copyright extension laws which are bought and paid for by large companies (it's nick-named the "Mickey Mouse Act" for a good reason...) is very bad for most of copyrighted works. A good example of this are out-of-print books in which neither the publisher nor the author has a commercial interest, but which are interesting to a niche of the public.
What happens is, of course, that Disney is very afraid that their copyright on the critter should expire, so they pay some politicians to fix American laws to extend copyright on
everything. No discrimination at all. I believe that Disney should be able to benefit from Mickey Mouse all they want as long as they have commercial interest in him, but with the current state of affairs there are severe consequences to other, less commercially interesting works.
For instance, a lot of old movies currently reside only as copies on old, fragile film rolls. They are still copyrighted, although no one distributes them, and very few people (except film buffs and historians) would be interested in them as of now. They certainly have no commercial value. The media they are recorded on degrades continually, and they will soon be lost. It's technically easy and cheap to store those movies digitally for future generations, but there's no practical way to do it legally, as it's extremely difficult to ensure that you have the permission from everyone involved to make a digital copy (basically most of the crew and actors, including stuntmen and stand-ins). Some are dead, others are simply impossible to identify and/or locate.
The same thing goes for a lot of older books, especially niche ones, printed in small runs and maybe on acid paper. They aren't converted for storage because no-one can do all the work of tracking down the copyright holders for all that material. There are exceptions for national libraries and the like, which can archive indiscriminately, but they can't possibly get physical access to, or even the resources to digitise all of them. Even if the books are physically durable they might be lost in obscure collections in some university's archive, or damaged in some manner.
Default copyright terms should be a lot shorter than they are (say, ten years), *unless* the copyright holders express an interest in keeping their copyright. This should involve, say, a trivial amount of yearly effort (like a submission of a form) and a relatively small fee, maybe regulated by the amount of income the work generated in the last year and the total age of the work. Works with a small income should be cheap to renew, while greater age should make renewal a bit more expensive. In this way a commercially viable creation would continue to generate income for its creators, while forgotten "orphans" would soon be free to the public.
My motivation for writing this longish post is that I feel that there are lots of publications, music and movies that will simply vanish from history because of the current laws. It's tragic that we have the technology, and a lot of enthusiasts willing to use it to preserve these things, but the laws preclude it. A man who's a lot smarter and more knowledgeable than me wrote a very insightful (free) book on the subject, check out
Free Culture by Lawrence Lessig. Several of the points in this posts are originally his.