If you buy this 3 cd set you get exactly what it says on the tin. 61 tracks released from 1957 to 1959 (in release date order not recording date order) plus a third disc of an interview with Ricky Nelson (which you probably won't play more than once).
The great James Burton plays guitar on most of the tracks, as notated in the very good 12 page booklet which accompanies the cd set.
Two versions of the excellent "Believe What You Say" are included - one with a vocal chorus overdub and in my opinion a far better version without.
All Ricky Nelson's best recordings are in this set. His only well-known hits not here are "Travelin' Man" and "Hello Mary Lou", which together made up a double "A" side single from 1961 (which is why it's not included).