It has been awhile since I took the CCNA exam – but I do recall that they are adaptive tests – so if you have a weak area – that’s going to get tested the hardest. I too just did book learning to take the exam – granted I was working with a CCIE at the time – so when I had concept issues, I could at least ask him. But from what I remember – they tend to cover all the main sections in the book. They had “labs” where you had to type in the correct configuration commands or hook up equipment properly. So knowing the syntax is important.
The bottom line is if you feel comfortable with your level of knowledge then take the test (If you can answer all the book tests 100%, then go for it) You may not pass the first time – but it will give you a look at the test and how it works and tell you what your weak points are so you can review them. Honestly – I think I took the stupid test 3 times before passing – each time was an improvement. There are sites out on the internet that provide some CCNA partial tests – they are a great place to test your knowledge (http://www.internetworktraining.com/ – don’t know anything about them – I only did a search)