Fly By Night may certainly be the easiest song in the pack, but I found it to be the most fun song to play. While half of the chart consists of chords, you're spending most of the time changing notes so you're hardly ever keeping one finger held down.
The verse riff is fairly easy, beginning with a few long 3-note chords before moving into a mix of moving single notes and two note chords. The only gripe I have with this chart lies in this riff where you frequently switch from a (RY) chord to a (BO) chord, but you may have an easier time with that.
The chorus riff has a higher chord/single note ratio than the verse riff, but as with the verse riff, you're still moving your fingers again. You'll get the moving part of the verse riff again right before moving back to the verse.
After playing through another verse and going back through the chorus, you'll come to the solo. As you would hope for when playing guitar, the solo is filled with HO/POs moving up and down the fretboard and is the hardest portion of the song. There's nothing too difficult in the solo, but it's still incredibly fun.
After the solo you'll get the chorus again and then the bridge. There's far fewer chords here than in the verse and chorus, but you're still moving up and down the fretboard. After this, you'll get the chorus one more time to close out the song.
All in all, this is definitely a chart any guitarist should pick up.