What books are you referring to?
If you like you can read “Conceiving the Inconceivable”.
Even after becoming a devotee of the Lord, the challenge to make the right choices still remain? How does one understand the choice that make is something inspired by the Lord? Is that by the outcome of the choice, favorable to devotional service?
Yes, choices are hard. A choice means a sacrifice of something less important for something more important. Generally, soma or our pleasure is sacrificed, for agni or a higher purpose. But this proves to be insufficient. So, God’s pleasure is prioritized over our pleasure. But some people also kill in the name of God’s pleasure. So, ultimately, we must know what pleases God, and that requires knowing God. Until one completely knows what God likes and dislikes, in what situation He will choose what, choices remain difficult. But at least the principle is God’s pleasure.
There is a system of philosophy called Mimamsa, which is devoted to the question: What is duty? Just like Vedanta starts by the aphorism, “Now, therefore, let’s inquire into Brahman”, similarly, Mimamsa begins by the proposition: “Now, therefore, let’s inquire into dharma”. It is by far the largest and most complex system of philosophy. Just as the simplified conclusion of Absolute Truth is Krishna, similarly, the simplified version of duty is the pleasure of Krishna.