I’m going to third the Cook’s Illustrated / America’s Test Kitchen suggestions. Some of my best cooking endeavours have been possible thanks to these two sources.
I strongly recommend Nigel Slater’s Appetite for relaxed, interesting, and delicious recipes. I’m not sure it’s an utter beginner’s cookbook- maybe second level- but nothing he makes is difficult.
And Laurie Colwin. Her two cookbooks. They’re amazing.