The penalty is death if they are christians converting to islam too.....alot of stories about that where i come from.......
Non-muslims are perfectly safe practicing their religions.....When islam entered any country it never forced anyone to convert and it never destroyed anything.......A good example would be when islam entered Egypt...christian Copts were being fed to the lions as entertainment for the Romans......Islam soon put a stop to that.......people were free to worship as they pleased.....
If Islam was not tolerant they would have destroyed the symbols of idolatry ...(All the statues of kings and gods the ancient Egyptians worshiped and the temples they worshiped in)....but they are around for all to see up to this very moment
If pagan temples were not destroyed certainly churchs and synagoges would be preserved...
Today we have churches in all the Arab countries that have christian populations....I know we have a Jewish temple in Cairo...granted it is heavely gaurded but that is because of the political stress we all know about....
Jews, Christians and Muslims have lived together amaicably for ages.

Marjorie....I greatly appreciate your interest...About your question ...Aisha has an excellent point, but I have a thought that came to me......well ofcourse Adam and Eve did not need a book because they communicated easily with god they were not far from his teachings, they repented for their sin and god forgave them.....Even when the worst sin was commited(Kane and Able ....Brother kills brother)they were close to god ...they knew him...
After generations people started tomove farther and farther away.....By the time of Noah They had turned to idolatry(for the first time).They made gods of their ancient long gone scholars and started to worship them...so Noah was there to try and teach them what they had forgotten .....
By the way there are more holy books then the torah and the bible...David had one....The rest are not mentioned as are alot of the messengers sent....Every now and then god would send a messenger and/or a prophet to remind people....some would return to the faith some would not ...others had to be totally innihialated because they were to far gone...until in the end of course it had to stop...there had to be a last prophet and messenger...a last book. .lili.