Hey Nick, i'll try to answer your question briefly and you can ask more questions after it. :)
What is Islam?
Islaam is a whole way of life so it covers every single aspect of our life. Whether it's on how to run a state (with justice), to the social relations on how to treat your friends, family (kindly, with respect etc.)
Let's start off with the fact that the majority of the world believes in a God, or 'Higher being.' The difference between islaam and all other faiths is that instead of just recognising that there is a God, we believe that the Creator created us with the purpose of submitting to Him, worshipping Him alone sincerely without any associates.
These associates can be stone idols, it can be humans (or human legislations) it can be a person's desires etc.
Islaam call's to the worship of God, known as Allaah in arabic. If you're confused about why God is Allaah in arabic, realise that people from spain call God - Dios, the french call God - Dieu etc. So there's nothing confusing about God being called Allaah in the arabic language.
Allaah has sent messengers to convey the same message of calling to the worship of God since the beginning of time, since Adam (peace be upon him) the first person to ever live. All the messengers came to call to Allaah's worship, and this is the purpose of our creation - to worship Allaah, without no associates, so no idols, no humans, no law which opposes the law which Allaah has revealed to His messengers.
We as muslims believe that Noah, Moses, Jesus, Muhammad (peace be upon them all) were prophets. There have been a total of 124,000 prophets that have come to mankind to call to the worship of Allaah Alone. However, the majority of mankind has fallen astray, because they do believe in a Creator, but they reject the fact that He should be worshipped alone.
Any deeds we do, we do them sincerely to gain Allaah's Mercy, and if we gain it - we will enter the eternal paradise which all the prophets have called to also. However, if someone rejects the worship of the One God - without any associates, they will be punished in the hellfire. This is the only sin which God does not forgive, why should He, if the person is saying that a stone is God? Or a human is God etc.
We all will die and be raised back on the day of recompense, when Allaah/God will judge between us on all that we did. No-one will be judged unfairly because Allaah is the Most Just. Allaah can bring the dead back to life, the same way He brings the dead land back to life by sending down rain.
If you feel that God is being unfair to His servants by punishing those that associate partners with Him, then the justice for this will also be balanced out. Allaah will ask those who associated partners with Him to ask the one's they worshipped for reward. So if someone worshipped a stone idol, they will ask that for recompense on the day of judgement (obviously the stone won't be able to do anything.) If someone worships a human, even if the human is pious, the person will have to get their reward from this human [but obviously everything is dependant on the Creator.] The one's who worshipped God Alone, sincerely without no associates - they will be rewarded by Allaah, the Exhalted with an eternal paradise where they can have all that they desire, and more.
If anyone feels that it is unjust, then they have to stop being unjust to their own Creator. If Allaah created man so he should serve Him especially, then why worship the stone idol, or why worship a human when you can turn towards your Creator and Provider?
The servant and final Messenger of God, Muhammad (peace be upon him) said that God Almighty says;
O My servants, I have forbidden oppression for Myself and have made it forbidden amongst you, so do not oppress one another. O My servants, all of you are astray except for those I have guided, so seek guidance of Me and I shall guide you, O My servants, all of you are hungry except for those I have fed, so seek food of Me and I shall feed you. O My servants, all of you are naked except for those I have clothed, so seek clothing of Me and I shall clothe you. O My servants, you sin by night and by day, and I forgive all sins, so seek forgiveness of Me and I shall forgive you. O My servants, you will not attain harming Me so as to harm Me, and will not attain benefitting Me so as to benefit Me.
O My servants, were the first of you and the last of you, the human of you and the jinn of you to be as pious as the most pious heart of any one man of you, that would not increase My kingdom in anything. O My servants, were the first of you and the last of you, the human of you and the jinn of you to be as wicked as the most wicked heart of any one man of you, that would not decrease My kingdom in anything. O My servants, were the first of you and the last of you, the human of you and the jinn of you to rise up in one place and make a request of Me, and were I to give everyone what he requested, that would not decrease what I have, any more that a needle decreases the sea if put into it. O My servants, it is but your deeds that I reckon up for you and then recompense you for, so let him who finds good, praise Allah, and let him who finds other than that, blame no one but himself.
It was related by Muslim (also by at-Tirmidhi and Ibn Majah)
To read up more about Islam, you can check this site out;
http://IslamReligion.com
I'm convinced of the truthfulness of Islam due to it's comprehensive nature, its caring nature, and the ability to have a perfect relationship with God and huiman kind at the same time. Islam allows you to reach newer levels you could never accomplish before, it allows you to believe in yourself and better yourself continuously. All this is done through following the wise guidance which has been given to us as a mercy.
So always call out from your heart; "God, if you exist - guide me to what you love and make me of the successful." Then listen to the guidance with an open heart and mind.