Assuming you have already read the previous (rather low) reviews on here, my own review may seem like overkill, but I feel that I must express just how bad Neamen's book is at explaining the material.
Most other reviewers have already covered the important points, so I'll just develop on two that I find particularly unsettling (after wasting several hours trying to see how the author arrived at the solution for ONE problem in his book): How is anyone supposed to figure out the many assumptions this guy makes when he makes no mention of them anywhere else? Also, how is anyone supposed to know what equations to use in what problems?
So far I've found that all the answers in the back of the book have been correct, however the problem is that the reader has to first figure out what equation(s) to use, which is why I'd imagine that many readers believe the answers to be incorrect. In terms of what the author explains, there are (presumably) several ways of obtaining the same answer, but for some reason this is not the case, given that your answer will often be different depending on what equation you use. Assuming the author is even correct in using the formulas he uses, he offers no explanation as to why one equation should be used in one situation but not in another.
Also, this book makes entirely too many assumptions and offers no explanation as to where they come from. Case in point: Problem 1 of Chapter 5 asks the reader to determine the drift current density in a semiconductor material under a certain set of conditions. Well, this is all fine and dandy, except for the fact that the author provides an in-book example IDENTICAL to the problem in which the answer is DIFFERENT. So why do the example and problem answers differ? Because Neamen (in the problem)apparently arbitrarily assumed a different value for electron mobility in said semiconductor material, yet he did not not explain why this different value was assumed in the first place, nor did he offer any clear explanation as to how to determine the supposedly correct electron mobility.
In summary, this book would be somewhat decent if the author spent more time explaining the material more clearly. As it stands, there are simply too many assumptions made and too few explanations for them, making this book a very poor source of information.