I find the recipes from JO's first book - the Naked Chef by far his best.
I've made nearly all of them and they are now all ones I can make without even thinking.
Perhaps because I was learning to cook and actually followed the recipes! I'm a very confident cook now and much more likely to adjust as I go along with whatever I have/don't have lying about.
Nigel Slater was great for getting me to substitute/add things/mix things up once you have the basics right.
So... very experienced, confident cook but almost every one of JO's 15 min and 30 min recipes were crap. A faff and not worth it and certainly not doable in the time he claims.
The only useful thing from both books was Pataks current paste )not sauce), especially the tikka masala one, is excellent and tastes better than mixing your own spices from scratch.
I live Nigella but she is better for sweet things IMO. The book I've made the most recipes from is Forever Summer - one of her earlier books.
I can't bake - as PP have said I'm too used to adding a bit here and there.
I can do reliable lemon drizzle, banana bread and carrot cake. The former and letter I elevate to pretty good with the addition of a fuckton of lemon drizzle and a LOT of cream cheese frosting!