while they are all good books, some of the information on techniques and patterns in The Gilley and similar books like the 2 Jack Shaw books (Tying flies for Trophy Trout & Fly Fish the Trout Lakes). Morris and Chan on Fly fishing Trout Lakes. Steve Raymond's Kamloops, may be a little dated these days. Trout School by Mark Hume and Mo Bradley published in 2019 would be worth checking out.
One thing we really lack in BC (and elsewhere I take it) is a general book on fishing the many larger lakes for trout, kokanee and char. There so many good lakes literally too many to mention from a few square miles to very large bodies of water like Kootenay lake (where I caught my PB rainbow - 22lb 14 ozs) Arrow Lake, Christina, Okanagan, Shuswap, Quesnel, Babine to name a very few. A book that goes over seasons, how to 'break a lake' down, lures trolling speeds, getting deep and shore fishing would be helpful to a lot of anglers.