Would the first book be valuable for someone in their late 20's? I'm fairly happy with what I've done this decade, but maybe I could apply the relevant stuff to my 30s...
[1] https://www.quora.com/I-am-in-my-late-20s-and-feel-I-have-wa...
Long answer: the sooner you read it the better, but any time is better than never. There was a great metaphor early in the book, actually. I don't have a copy on hand so to paraphrase: your life is like a cross-continent flight. If you want to change your destination, earlier on is better--the plane need only make a slight adjustment at the beginning to alter its trajectory significantly. Closer to the end, and you gotta make a pretty sharp turn.
It's not the perfect metaphor but for me personally it really resonated.
Especially if you're fairly happy at your late 20's, any adjustments you might discover you want to make probably aren't that far off :)
So if you felt fairly happy chances are good you’ve made good choices. It may be worth a read for anything you’d like to tweak