Kelson was an excellent angler and superb fly tyer. He was also quite vocal when someone challenged him or began writing or telling others that there was only one way to catch salmon. He was also well-educated and when combined with his penchant for simply telling it like it was even if the hearer or reader got offended didn't sit well with the politeness expected of well-educated men of his era. Needless to say, this didn't endear him to some.
Additionally, he didn't suffer fools, or those who hadn't all the experience fishing for and catching salmon or tying salmon flies that he did, well at all. He had a penchant for simply telling them they didn't know what they were talking about, which didn't gain him any friends either. For example, although he listed a huge number of fly dressings in his book, he himself stated throughout that he only used a few dozen in his own fishing. And he committed one of the major sins of the era, he used flies designed for one particular river on other rivers and caught salmon doing so.
He was excluded from participating in and entering salmon flies in some major tying competitions after his falling out with Marlow. And since Marlow was a publisher, he used his publishing company to in effect black-ball Kelson. Kelson wasn't excluded because he was not a world-class tyer at the time, he was excluded simply because the major sponsor didn't want him to participate.
One of his best friends and angling companions was Major Traherne, a consumate gentlemen, excellent fisher, fly tyer, and creator of the Traherne series of rather complicated and difficult to tie flies. If you read his book, you find he gives credit to who originated the pattern, if he knew. And you will also find much very useful information on fishing for salmon and what works and his opinion on what doesn't. You will also find that a lot of the stuff written about him over the years since his death that he supposedly wrote is pure make believe.
In my opinion, there has been much published over the years about how Kelson was a boorish rogue and bully, but I strongly suspect this is the result of folks simply parroting what they read without really knowing much about the man himself. Personally, I would have loved to have met the man if for nothing else, his great knowledge of salmon angling and salmon fly tying.
I also rank his book as the most important one on salmon flies and salmon fishing. I think the next most important one on salmon flies is Price-Tannat's book. Hale is a great book on tying, but I'd rank it third in importance of books on salmon flies. Hale along with Hardy has a huge number of dressings. But Kelson's bood predated theirs and their books (Hale's first edition didn't have all those flies in it, they were added to editions after Hardy's book was published) include all the flies Kelson lists. And the next most important one a salmon fishing and salmon flies is Traverner. I'm sure some will disagree with me on this, but that's fine and of no real consequence.
Before someone takes offense at not including Blacker, his was a great book, still is, but it is not easy to understand his tying instructions. This I'm convinced is the direct result of two things: 1) Blacker didn't want to tell everyone how he did things in order to protect his professional tying interests; and 2) the editor altering some of his language before it was printed. Blacker was not a well-educated man, so I'm sure his writing was in dire need of editing. Unfortunately, I doubt if the editor knew much if anything about tying married wing flies resulting in some odd directions that would serve to greatly confuse folks unless they had some experience tying married wing flies.