The Justice League is a complicated mixture of heroes and personalities that has gone through many variations in its membership during their many incarnations. There's always a League dynamic, as they're supposed to be humanity's first and last line of defense, but the characters on their roster have changed so frequently over the years that you'll get a very different experience from book to book and era to era. The concept of the greatest heroes in the DC Universe teaming together makes it more than worth reading, if you know where to start.