Here is the Panzer Colors errata sheet;
http://web.archive.org/web/20010811223829/www.geocities.com/Baja/1654/errors.html
Even with reputable publishers, the accuracy of the text and photos can range from excellent to deplorable, depending on the author. $100 tomes from the highly respected JJ Fedorowicz Publishing Co. can have all sorts of typos, mistaken photo captions and grammatical errors. At least Fedorowicz will actually take the time and effort to correct their errors and post their errata sheets on their website, a lot of publishers don't even bother.
This is a huge can of worms, probably the largest one we have to deal with in this hobby. It pays to know who your authors are ahead of time, least you end up buying books that are good for little more than a booster seat for your kids. Usually, if a book is a real stinker, it will show up in the customer reviews on Amazon.com. This is usually a good place to start if you are unsure about a particular title.