Every book is going to have it's advantages and disadvantages. I've used Gleim, ASA, Jepp, Machado, King Schools (same thing as the Cessna kits), as well as the FAA books.
My opinion:
Gleim is the driest of the group but it's purpose is to be straight forward. So your students will get pretty much exactly what they need but you may loose them with lack of colorful pictures. I'm a picture person, so they lost me. You do have an advantage of the CFI discount though. They called me the other day and I had to turn it down because King Schools offers Cessna pilot Centers discounts too which I'm a part of. I'm not sure what their discounts are for CFIs, 20% comes to mind but I could be wrong. I do admit though, I liked their customer service. One of their CSRs called the school and we talked about what it was like to be a CFI and fly in nebraska more than the actual discount. I appreciated that even if it was just trying to get on my good side. As soon as it's all about buying something, you loose me as a customer.
As a student, ASA has my favorite DVD course. The Private pilot books themselves are just as interesting/dry as any other text book of its size but the DVD courses are the least boring I've come across, king is a close second. I recommend the written study guides to all of my students. I really like the explanations and questions grouped together as well as the inclusion of the actual test supplement just like you will use on your test. All of my students have used this way to study for their writtens, I haven't heard any complaints.
Jeppesen is great and I have used them as a college text book for both my instrument/commercial as well as Multi. These books are awesome with tons of pictures and explanations. The drawback is they're very expensive and sometimes their size can be a bit intimidating. The private pilot book will run you about $85. You might be lucky to find a used one online since many colleges do use them. If you want to use Jepp, the cheapest route is just to buy the whole kit.
King/Cessna is what we use at the flight school. Most of their programs are online now which is great for people that love computer based training and hate taking a huge text book everywhere. The videos we're all used to are still included in chunks throughout the program. All of the info including all of the FAA's books are in PDF format along with practice exams are in there as well. King is pretty good and the Kings themselves are great people (I've met them!) but sometimes I feel like I'm being talked to like a 5 year old. We don't use any books from them so I don't have any recommendations for that. A huge advantage is that the online programs are good for life and will also be updated for life too so you can always go back and review years after your training (which is awesome for flight review time!) The "line up and wait" was added a week after the rule took place. The drawback is that you do not get an actual textbook since it's all online and it's also a little pricey. You do get a lot for your money though. I like the handiness and everything that's included like all of those FAA books, a cessna POH (which is about $60 or so) and the ability for your instructor to link with your program to see how you're doing. The entire kit is $349. You can check out a free demo online.
http://cessnaflighttraining.kingschools.com/demo/
Machado is an awesome all around book. You get the great explanations similar to Jeppesen, the weather section in one book unlike the FAA's, it had enough pictures to keep many students following along, and some great humor to keep them interested. It's not the cheapest out there but I believe as far as hard back quality books, it's a good investment. I've taught ground school classes using this book and the knowledge the students get get is well rounded. Machado's book is about $65 brand new.
As an instructor, the FAA books are my personal favorite. The Airplane flying handbook is great for understanding the maneuvers in textual format. That's the "flying" stuff book. The Aeronautical Knowledge book is the book I refer to most of the time for good knowledge based information. It's very pictorial and really not as dry as I originally thought when I bought them. It's the cheapest of the books you'll find and what's even better is many times you can buy them at Barns & Noble or any other large local book store. I haven't bought the weather book but I have heard it's lacking on some things. If you guys run across a good all around weather book, I'd be interested in knowing. I've taught weather pretty well just using online resources, a combination of the above books, and real life experiences. All of the previous books/programs mentioned do have lessons on weather anyways. The FAA's books are about $25 a piece (or free online).
The FAR/AIM, well that just speaks for itself. Just get one.
I get asked this same question all the time, "which books are right for me?" The ultimate answer is to check out the pros and cons of each, take a look at the books, and just decide what kind of a learner you (or the student) is. If you want straight forward, cheap and don't care about dryness, go with gleim. If you want lot's of pictures and deep explanations, Machado, King, or Jepp are good choices. The FAA books are somewhere in the middle. I'm lucky in my training history to have used all of them. I use a combination of ASA, Cessna/King, and the FAA's books in my daily instruction. Use what you like though, they're all going to give you the same information just in different formats.
p.s. Another good book to have as a reference is Everything Explained for the Professional pilot... it's nice fun dictionary.
Hope this helps.
