"the best of it" (39:18)

[Elena]

Thinking aloud voice.

this verse implies

1-some of the things said in The Book are better/prefereable than others;
we have to discern which ones are what we have to follow/perform; we have been given freedom to feel which ones are the best

or

2-the best are unchangeable + the compound of all of them is the key and the verse is refering to our duty of being aware of the best

and

it seems the message in The Book is not clearly explicited but little difficult to interpret to spur our mind.

Maybe there are other points from your understanding. If any of you feel like to comment, thank you.