recommend not using Nexus Mod Manager. To install AOM without it, simply download part one and then drag and drop the data to your steam/steamapps/common/skyrim folder. Then do the same for part two. 99% of download errors are due to NMM. If you must use NMM, follow the instructions posted below.

WHEN UPDATING: Uninstall all old AOM files first (especially the ARTOFMAGIC.esp). When updating from 7.8 - 8.0 a clean save in not neccessary. Just uninstall 7.8's multiple files and install 8.0's single file and play. All items, except the orb of eyes, will still be there.