I like Todd Lammle, and overall, I like his CCNA book. His approach is very casual, as many have said. It is written as though he is talking to you, and that does hold one's attention better. If you are brand new to networking, or just have Net+ level knowledge, then this is by far the best book out there to bring your personal knowledge up.
That said, if you are using this book as your sole resource to study for, take, and pass the CCNA, you will be obliterated....even if you are in a Cisco networking profession. The problem is that the information provided in this book, while again, excellent for increasing and familiarizing yourself beyond Net+, is not enough alone to get you through the actual difficulty and content of the test.
I began studying with this book 3 years into my network engineering career (mind you, I do not have a technical academic background, and found this passion post-college). I read this book cover-to-cover, highlighting anything I found remotely important. I then re-read the book a 2nd time immediately, mostly the information I highlighted on my first read, being sure to ask mentors anything I was uncertain about. There are 1-3 assessment tests after every chapter. I took every test in the book until I passed all of them 100%.
Because the CCNA has such a punishing failure rate (88% chance you will fail the first attempt), and costs $300 each attempt, I felt I had better be safe and pick up a few more resources; CCNA Exam Cram by Jeremy Cioara, for example. Right away I noticed the assessment tests were much more challenging than Todd's tests, and was failing most sections (by Cisco's standards, which is anything below 86% correct). I did the same thing with Jeremy's book - Practiced all 330 questions until I understood the "why?" for each and could consistently pass by Cisco's standards.
But then I was faced with a thought; If Todd's book isn't enough, what if Jeremy's isn't enough also? I chose to buy one more resource, and while the increased difficulty slope wasn't quite as high from Jeremy's material to this material as Todd's to Jeremy's was, it was still enough that I was scoring under 86% again (78% on average). Did the same thing here. Took these tests hundreds of times, referencing Todd's book, Jeremy's book and mentor advice on anything I got wrong, and scheduled the test after I could pass 100% of all test material I had accumulated.
I passed with a 98.6% in March of 2012 on my first try, after about a year of non-stop study and 4 years on the job experience. My point in all of this; There is no "1" piece of material that will solely prepare you to pass the CCNA. This exam is a ton of work and requires multiple resources. Expect to spend $100-$300 on resource material (plus the $300 to take the test) if you want to competently pass. It will pay for itself when you land the job you wouldn't have before being certified. For the sake of preventing people from skipping steps and cutting corners, I will not disclose the most challenging resource material I purchased. We have enough fakes in this industry. Learn and comprehend the material.
In closing, Todd's book is an excellent preliminary/1st step in beginning the CCNA study/comprehension process. Purchase it, read it twice, take the assessments hundreds of times. Purchase the Cisco Press CCNA book by Wendell Odom...read it once, take the assessments until you can pass them all. Purchase 2-3 practice test resources WITH EXPLANATIONS, and take every one until you can consistently pass all the material you own. Then schedule the test, and you should pass on the first try.
Back to my original thought though, if you just want to casually increase your knowledge with no plans to take the test or just have some standard-issue reference material on hand, then this is the best material available.