Where abouts do you live? If in Sydney i suggest you go to Kinokuniya on George St, they have multiple copies of all currently released volumes. I picked up 3 volumes the other day from them at $13.90 each. If elsewhere in Australia, you can order off
http://www.cartoongallery.com.au, or there are most likely a few comic book stores around that will stock the books.
As for reading order, you don't have to start with #1, and different releases of the Atom mange are complied differently (i have 6 and 11 of the Japanese white books and the stories in them are ina totally different order to the darkhorse released manga). i have volumes 1-5 and so far the manga story order seems pretty good. For collection purposes what better place to start than #1 ^_^