I'm reading Posner's The Little Book of Plagiarism. "Reading" may not even be the right way to put it, since the book is so small (109 pages and pocket-sized) that I nearly finished it in one round-trip commute. (Don't worry--I take the train.)
I'd definitely recommend the book to any writer, publisher, editor, or even blogger. Aside from the fact that it's a quick and interesting read and not at all like the legal treatise it could be (and haven't we all wanted to peek inside the comparisons between Kaavya Viswanathan's writing and Megan McCafferty's?), it's full of things that we should be thinking about as we make writing and publishing decisions. Plagiarism isn't quite so straightforward as it might seem, as evidenced by some of the respected authors and scholars who've been called out for it.
For instance, did you know it was considered plagiarism to cite a source you found referenced in another source without citing the place you found it as well? Poor practice and risky, certainly, but plagiarism? Frankly, I didn't know that, and I'm both a writer and an attorney.
It's good information, and it only takes a minute (well, a couple of hours, then) to read. And if it gets you interested in all issues plagiarism, you'll also want to check out Jonathan Bailey's Plagiarism Today blog. I don't know Jonathan, but he happened to leave a comment on my post about Eggs, Milk, Vodka last week that coincidentally had me checking his blog on the same day I checked out Posner's little book. It was a happy coincidence and he went straight into my bookmarks.