I have seen that other harmonic authors focus mainly on the price Fibonacci relationships and PRZ definition. I approach harmonics pretty differently. For me the key is the proper market position and harmony defined as price x time, not just as price. Many examples from Scott book do not look harmonic to my eyes at all, and to add they are not considering multitimeframe impact on the pattern structure. Anyway, every trader will approach it differently and every trader must combine it with proper MM and psyche-mind harmony if wants to be successful.
Regarding the books, yeah, you have seen this one probably already ->
Books on the Gartley pattern
I think the material gathered on this Forum goes in many aspects much farther than any of them (for sure in terms of spotting the proper pattern, but not enough yet regarding the MM, position sizing and entry techniques). As you know I am the author and architect of korHarmonics and AMP indicator, so regarding spotting the best patterns I know things.