Overall I think these books are well worth it and I would recommend them to others. The CIA exam is not overly difficult, but it does require studying. My workplace had the Gleim materials for free, but after looking at them, I didn't like them--I found the Wiley books easier to work with. I found that a lot of the questions in the Wiley materials were exact questions from the exam. I recommend not reading the actual materials, but just ripping out the pages with questions, highlighting the answers, and then reviewing those on a daily basis. I studied for about an hour or so every night, and I was able to pass parts 1 and 2 using about 2 weeks each, part 4 using about 1 week, and part 3 using about 4 to 5 weeks.