"Don't Waste Your Life" by John Piper is the latter. It's a powerful book that deserves your attention.
Here's one of the best quotes from the book.
"You don't have to know a lot of things for your life to make a lasting difference in the world. But you do have to know the few great things that matter, perhaps just one, and then be willing to live and die for them. The people that make a durable difference in the world are not the people who have mastered many things, but who have been mastered by one great thing. If you want your life to count, if you want the ripple effect of the pebbles you drop to become waves that reach the ends of the earth and roll on into eternity, you don't need to have a high IQ. You don't have to have good looks or riches or come from a fine family or a fine school. Instead you have to know a few great, majestic, unchanging, obvious, simple, glorious things - or one great all-embracing thing - and be set on fire by them." John Piper, Don't Waste Your Life, page 44