Ive got a couple versions of the lincoln book, and like any engineering book written by a company that makes products related to the subject, is biased. The information is good, but heavily leaning towards electric welding ( for obvious reasons ). The Linde books leaned towards OA welding, again for obvious reasons. Somewhere in between lies a happy truth. The AWS I have found to be biased as well many times, as the people sitting on the councils are usually equipment industry people. The ASM seems to be the best independent source. The further you dig into this subject, the more confusing things seem, until you hit the point where you start questioning the motives of textbook writers, then it all becomes pretty simple.