Now, karma will see that I make several spelling and grammatical errors of my own in this post but anyway... Do you find that there are too many expensive textbooks from well known publishing houses that are choc full of typos? You might pay around $100 for a 'good' book on op-amps that comes with high recommendations only to find that there are many errors that see you wasting time trying to comprehend a circuit that just doesn't add up. At first you think it must be correct, and that you simply don't understand the new concepts being explained. But after checking with colleagues or other similar books (or here!) you realize the book is wrong. OK, so a typo or two in a book of 1000 pages is nothing bad but in recent years I'm starting to find that some books remind me of those old 'What's Wrong With This Picture?' cartoons where mistakes were deliberately drawn in and you had to count as many as you could find. Many of these books appear to be part of the curriculum taught at universities. So I wonder if they are written specifically to just cover the syllabus and secure sales based on their chapter headings. Perhaps it's just too expensive these days to have a proof reader with technical knowledge on the subject to read through it.