The gleim book is made from required material by the FAA. It is derived from many different sources. The aircraft manual is one source that is made by the manufacturer. It does not come from 50+ different books that we need to learn an aircraft. The manual we carry, is not always the same as the manual that is produced by the factory. The manual we carry DOES have every bit of info about the aircraft. I am not camparing the two as a study guide, I am comparing them by the information they cover and what is required to take a test or perform a function of the everyday operation of the aircraft. I know what I am trying to say is a little confusing unless you think of it as I do. There are many differences between a gleim book and an aircraft manual. The point is that ALL the info you need to pass you test, is in that aircraft manual, just as all the information you need to pass the FAA written is in the gleim manual. Yes there could be more in depth info in an aircraft manual that is not publihed. There is also more info about an ILS in an Instrument flying handbook than there is on the FAA exam. All I am really trying to get across is why is it so hard to actually study for a test, than it is to try to make shortcuts that will eventually catch up with you.