Among the many laughable errors in the Security+ All-in-One Exam Guide, my favorite comes in chapter 18, on risk managment. It comes on page 488, in figure 18-7, where we are trying to calculate which security problems are most important to fix. "Cost to fix" and "difficulty to fix" should _subtract_ from the total score for a problem, not add to it, since the more expensive or difficult a problem is to fix, the _less_ likely it makes economic sense to fix it. That an error as fundamental as this could slip by shows how poorly this book was edited.
All in all, this is a disastrously bad book. To some degree, too many cooks have spoiled the soup (the book has several co-authors, and they seem not to have read each others' contributions). There's an immense amount of duplication of material, while at the same time there are many terms and concepts that are invoked without ever being defined. At the least, this book should state that a reader needs a casual familiarity with networking (equivalent to that required by the Network+ exam, which I passed) to have any hope of understanding a good 40% of the book's material.
The only valuable chapters are the ones on security baselines (specifically the info on operating system and application hardening), cryptography (though much of the math used there is not explained), and public key infrastructures--conveniently, these are chapters 9 through 11.
Though this is the only Security+ book I have read, I feel confident in recommending any other book over it.