Advanced book collectors occasionally find that the most recent object of their desire, a book for which they paid good money in good faith, is stolen property:
Depending on the laws of the locale where the theft occurred, the collector may or may not have to return the book to its rightful owner, and the collector may or may not be compensated for his or her loss (often by sticking the bookseller with the loss).
More often than not, the theft was not from another private collector, but from an institution such as an academic or major public library. Because such thefts generally are under-reported by such institutions (for fear of embarrassment, as well as the fact that such thefts are not likely to endear the institution to potential donors), and because laws regarding book theft usually are pitifully non-deterrent, it often is difficult to know in advance whether or not one's most recent purchase may be problematical.
As shameful as book theft is to most serious collectors, what is far more shameful is that so many book thieves do not steal an entire book, but only the part(s) of a book that they need to improve their collection (a map, a title page, etc.). It is these types of book thefts that most often percolate up through the global miasma of infotainment and into the consciousness of the general public.
There are ways, though, that collectors can protect themselves. The first is to exercise a little common sense. Just as no one is likely to sell you a real Rolex for $10, so it is that the real owner of a First Edition, First Printing of The Great Gatsby is unlikely to sell that to you for $10.
Second, buy from booksellers with well-established reputations who belong to organizations with ethical codes of conduct that protect the book collector should a purchase "go bad" (for whatever reason). See the links in the left-hand column of this blog for some of the more notable such organizations (ABAA, ILAB, IOBA, etc.)
Third, keep an out eye for publicity about stolen items that are issued by organizations such as the Museum Security Network (see the link in the right-hand column of this blog under Bookish BlogRoll).
Fourth, make sure your own, private library is well protected against theft. If your collection is worth the investment, institutional-grade systems can be installed to protect your library. You also may want to consult the American Library Association's Guidelines for the Security of Rare Books, Manuscripts and Other Special Collections for additional ideas should the value of your private library warrant such measures.
At a minimum, you should consider keeping a photographic record of your library. And make sure that it is well-insured. Most homeowner insurance policies are inadequate for this purpose: consider adding a rider to such policy, or take out a policy specifically designed for this risk.
(Curses inserted into one's books generally are ineffective, witness this supposedly apocryphal, but since disproved, medieval book curse):
For him that Stealeth a Book from this Library,
Let it change into a Serpent in his hand & rend him.
Let him be struck with Palsy, & all his Members blasted.
Let him languish in Pain crying aloud for Mercy,
Let there be no Surcease to his Agony till he sink to Dissolution.
Let Bookworms gnaw his Entrails in token of the Worm that dieth not,
When at last he goeth to his final Punishment,
Let the flames of hell consume him for ever & aye....