In my advanced E&M course, PHYS-4400, we've run into one of the great walls of Physics teaching. The textbook which had been ordered for the course before I was assigned to teach it, is really more of a graduate level book. Which is a shame, since Brau tries to incorporate relativity into E&M, which I very much approve of. So we've sort of punted back down to Griffiths, which had been the previous textbook.
Now I know of Griffiths reputation as a textbook. And from my work with it the last few weeks, I am pretty pleased with quite a number of the ways he does things, as well as the sometimes grumpy commentaries and footnotes. (grin) Of course when I took this level of course at Northwestern back in the late 70s, we used Lorrain & Corson, I believe, and at Michigan Tech in the mid-80s, they used Ruth, Milford & Christy. Everyone, it seems, uses Jackson at the graduate level -- one of the great textbooks of all times, despite the ridiculously hard problems and the sometimes obscure and dense writing.
The problems, as you can imagine in this Internet world, of having "industry standard" textbooks used by many, many institutions, is that problems, solutions, hints and even the publisher's solution manuals for Griffiths and Jackson have leaked onto the web. Now you or I know that just copying over someone else's answers to a problem is wrought with dangers -- if you don't know what you're doing then you rarely write things / copy them over exactly as they were sitting before you and/or you miss crucial steps which, if called upon, you will be totally unable to explain. Plus you're not helping your studying for exams. And you're cheating. And it's unfair to those who've slogged through a solution to be competing with cheaters. Etc., etc., etc.
The Single Source Problem
But it's kind of worse than that. Recently we were talking about the bar electret, an interesting sort of polarized material with a permanent charge of ±q on the ends -- essentially the electric equivalent of a bar magnet. Barium titanate, BaTiO3, was listed as one such material. I thought I'd look up on this to find out what sort of uses one has for a bar electret.¹ But if you try to look up "bar electret" in Wikipedia, one of the articles you'll get is about the Electric Displacement vector, D, where you find that the citation is Griffiths, Intro to Electrodynamics, 3rd edition. (grin)
Then a student came to me today and said that they had to show me this web page, because it'd left them uncomfortable. To work a problem sketching the electric field of a bar electret, they'd gone searching on the web -- and found someone's online lecture notes. Except that instead of talking about bar electrets, they just gave the solution to that particular problem in Griffiths.
If I wasn't already aware of the problem, I'd be upset. As it is, I just sigh. And regret that, at least in terms of high rankings in Google searches, no one else besides Griffiths is talking about bar electrets. Eventually you can get into a circular argument sort of situation, if you aren't careful, in which any confirmation you try to find on a subject ends up being cited back to the original source. And that's not good.
This is why we have to have more than one textbook. This is why we need faculty to write more textbooks, even though there are ones which "everyone uses". Because you shouldn't have just a single source on intellectual information. You need to have other references. You need to see how other people work the same material and types of problems differently. You need to have more than one source for preparing lecture materials.
Even if few people end up using these others texts in their courses, because after all, Griffiths at the advanced undergraduate level and Jackson at the grad level are the industry standard textbooks, and "everyone" is using them.
¹ The best use I can come up with, and I don't even know if it'd work, since I don't know anything about the strength of this charges, would be to electrically ruffle the fur of my cat without touching them. (grin)