Magento has the features that made osCommerce popular, plus cool features found on million-dollar sites of large companies like Circuit City or Target like zoom and pan on product images, perform product searches and get dynamic product suggestions. Magento is open source ecommerce, not based directly on osCommerce.
If you are an intermediate to advanced user who wants a program that can grow with you, then this is the right program for you. You don't have to learn all or any of the add-ons until you are ready.
WHICH BOOK SHOULD I GET?
Most users should try the MANUAL FOR MAGENTO USERS.
If you hate technical stuff, get the easy MANAGING AN ONLINE BUSINESS.
If you want to learn valuable power tools to make running your Magento store easier and faster, get USING POWER TOOLS.