This song has been around so long that we don't know who first wrote it. We'll look at the 1964 version from "The Animals".

Take a close look at the length of the notes in the arpeggio here, that's where the difficulty of this song comes from.

The song spends almost the entirety of it's runtime on the same chord progression! We do at times switch to a bridge where the chord progression continues, but we play it as triads on the top 3 strings. 

Notice how you can still feel the chord changes here with only 3 notes being played.

The real song has some variations in the chord progressions throughout, but these sections are enough for us to work with!