So you probably didn't expect to have to read to understand wrestling, but it helps greatly. One of my favorites is Pro Wrestling Illustrated, a classic magazine that comprehenses everything a true wrestling fan needs to know. It covers WWE, TNA, and most of the independents. It also contains wrestling cards, results, rankings, and title changes.
Another is the 2-in-1 Inside Wrestling and The Wrestler. They are published by the same people that publish PWI, and they cover the same things but have different information.
Both of these magazines are very informative and well written, and I also love all the pictures (which I cut out, laminate, and use to make collages on my wall). These magazines are sort of wrestling bibles, because they seem to have everything in them.
For all you WWE fans, you NEED to purchase the WWE Encyclopedia, which has a bio for every wrestler, title, pay-per-view, match type, and tag team in WWE history (and back a little ways).
The PWI Almanac is another good thing to buy at the end of the year or beginning (whenever it comes out) because it has stats, results, and everything else on all the wrestlers.
Invest in some quality wrestling reading!