You can build a rifle by "trial and error", but it is gonna cost you, or your gonna have something that only resembles a rifle. Get the other books, read them ,and then read them again. Once you understand how everything has to work "together", you then can understand how a small change in one location can effect other things in other locations on that firearm. Some things you will learn the hard way, we've all been there and done that, but you have to have a plan. I would suggest (and have done this with other people), make a list of each thing that needs to be done from beginning to end, most of the books give you an idea of what order to do these things, then follow that list as you build crossing them off your list as you finish them. Think things thru.