The thickest magazine appears to be a particular issue of Vogue and the smallest a kids magazine the size of a blood clot (one hopes they published a version readable by the human eye)
Circulation of three million or more
12.Ladies' Home Journal
10. Woman's Day
8. National Geographic
7. Family Circle
6. Reader's Digest
5. Good Housekeeping
4. Better Homes and Gardens
3. Game Informer
2. AARP Bulletin
1. AARP Magazine
These make sense to me in that order: being a lapsed gamer, I didn't know of Game Informer and as for the AARPs, not a clue.
It's fairly hard to conceive of a magazine shifting 22,200,000+ units, especially ones that carry no brand recognition in this part of the world. But what was the last Alan Jackson record you listened to? That's right, "Who now?"
Now that list is based on sales and there's an honesty to that because, if money was to exchange hands, neither the Bible nor Mao's Little Red Book would have been that widespread. If you base it on circulation, however, most of the above are still on the list. The two big additions are the Jehovah's Witness publications
Awake! published in 99 languages with a total circulation of 43.5 million copies
The Watchtower published in 203 languages with a monthly circulation of a massive 45 million copies.