People have presented arguments all different ways about the Bible questioning how it can apply in any way today. I've been asked why I should go by a book that's out of date, over 2000 years old; I've also been asked why we should go by a newer book like the Bible when more ancient religions were developed closer to creation itself.
The main reason the Bible still applies is that people are still the same. We require laws and consequences, we need guidelines on how to treat each other, and we need guidelines on how to set up a successful society. The specifics in the scripture don't apply to every society today but the principles they come from certainly do. Things like being required to help even an enemy get an ox out of a ditch may never be a situation you come across but helping someone get his car out of a ditch may. Though if you DO come across someone whose ox has fallen into a ditch, I can't imagine a reason you would not feel obligated to try and help.
Many have trouble when reading things like this:
When a man sells his daughter as a slave, she will not be freed at the end of six years as the men are. If she does not please the man who bought her, he may allow her to be bought back again. But he is not allowed to sell her to foreigners, since he is the one who broke the contract with her. And if the slave girl's owner arranges for her to marry his son, he may no longer treat her as a slave girl, but he must treat her as his daughter. If he himself marries her and then takes another wife, he may not reduce her food or clothing or fail to sleep with her as his wife. If he fails in any of these three ways, she may leave as a free woman without making any payment. (Exodus 21:7-11 NLT)
I'm sure anyone in America or other western societies have a serious problem with this. But it's not like it seems now anyway. For one, we have to consider that Moses wrote it and it was applied to a lifestyle where an unmarried woman had no real recourse to anything but being cared for by some man. Instead of "taking" women and discarding them when they were tired of them, these men were taught that women must be taken care of one way or another.
The verses where a raped woman is required to be married to her attacker gives me the creeps but since a woman was considered ruined and would be left uncared for from then on, a man needed to think twice before raping someone. He doesn't get to just apologize or go to jail for a while then be done with it while the woman has been destroyed forever. He has to marry her and take care of her for the rest of his life. Yes, it's still a horrible nightmare for the woman but the only feasible best option is that no man rape a woman in the first place. Since that won't ever happen, this was a protection for women. Is it really so much better now that a woman has to pay taxes and support the man in jail? (I think yes to that, at least she doesn't have to see him again but it's better if he has to pay for all her therapy if she chooses it, pay to support her at least as long as she's too traumatized to work, etc. If a woman takes advantage of it, oh well, guess he'll know better next time. Scripture requires a man to provide for his victim.)
There are other issues, slavery for one. People are in slavery in the world now, don't know why people act like the bible specifically condones slavery, it merely addresses slavery. Being kidnapped and held as a sex slave wasn't the issue in the bible so the instructions for slaves and masters there don't apply; these are for a society where it's expected or at least accepted. And if we're all honest, we have to admit that there are people in America that would be better off as slaves than not - the ones who can't manage to care for themselves but don't mind being told exactly what to do because decisions are beyond them.
Health concerns are addressed as well, before anyone knew about germs, the Jews knew to use running water and how to make antibacterial soap (germ killing soap anyway, is there a difference?) Certain foods were to be avoided, pork for example. It's probably wise to continue to avoid these things, there may be other reasons than simply that they were unsafe in that area at that time due to lack of refrigeration and the swine diet. For some reason, people decided that following these health instructions made them not just healthy, but holy; that caused some trouble. Right in scripture it says that as long as you follow these laws, I will keep you from the diseases of the (surrounding peoples). Their good health was meant to be an indication of the power and glory of their God to the other people.
The only problem I can see about the OT is that when I AM gave a revelation or instruction to a prophet, people seemed to take everything that person said from then on as directly from the mouth of God. Perhaps they were meant to but only if the prophet refrained from ever speaking his own words as they were supposed to. Can you imagine how difficult that would be?