I actually read these two books quite a while ago (about, oh, two weeks) but between school books, procrastination, and a lovely trip to Texas :) it has been put off till now. Therefore, I'm going to group them together.
I definitely think it's amazing reading books right through, because you really pick up the author's style and certain points they're trying to emphasize. Then again, it may be that Saul and David's lives were picked out by God to carry these themes as a lesson. Who knows. What matters is, there is a definite theme that carries through these books and is a valuable lesson to all of us: Giving God the control.
It shows up a lot when they murder someone (or don't).
When David and Saul are chasing each other around in 1 Sam 24, David says "May the Lord judge between you and me. And may the Lord avenge the wrongs you have done to me, but my had will not touch you." (v. 12)
When Nabal is rude to David, and God kills Nabal, David says "Praise be to the Lord, who has upheld my cause against Nabal for treating me with contempt. he has kept his servant from doing wrong and has brought Nabal's wrongdoing down on his own head." (1 Sam 25:39)
When David spares Saul's life again, he says "Don't destroy him! Who can lay a hand on the Lord's anointed and be guiltlss? As surely as the Lord lives," he sad, "the Lord himself will strike him; either his time will come and he will die, or he will go into battle and perish. But the Lord fobid that I should lay a hnd on the Lord's anointed." (1 Sam 26:9-11)
When Saul, David's enemy, is murdered, David killed the man who murdered him. (2 Sam 1)
Later, when men murder Ish-Bosheth (Saul's son), David says, "As surely as the Lord lives, who has delivered me out of all trouble, when a man told me, 'Saul is dead' and thought he was bringing good news, I seized him and put him to death in Ziklag. That was the reward I gave him for his news! How much more- when wicked men have killed an innocent man in his on house and on his bed- should I not now demand his blood from your hand and rid the earth of you!" (2 Samuel 4:9-11)
The theme is, [out of context] "The Lord will do what is good in his sight." (2 Sam 10:12)
Constantly, David is looking for the right thing to do in God's eyes, not man's. Yes, Saul was wicked, but David knew that it was not in his place to carry out that killing. Furthermore he is just, and punishes the man that does end up killing Saul.
So what does this mean for us? It takes a lot of faith to just leave things up to God, as well as patience, but I believe it's a reminder to be the "bigger person." Personal justice (I'm not getting into the judicial system here) should not be left up to the individual, but to God.
Picture used by permission. http://www.flickr.com/photos/chefranden/419290851/