Wow, what an album! Listen to the energy, the sheer joy of playing that the Duke and his orchestra exude in each and every single bar. The solos are incredible, and the warmth of the music is totally engaging. As the review above notes, this is a real mix of music, from the 60's way back to the 30's, but as was common with Ellington, he reworked pieces continuously in concert so that they are fresh and exciting years later.
This is actually a great introduction to Ellington - the tunes are there, the players are there, the man himself is on fine form, and the sound quality is superb. On a personal note, although I have an affection for big bands, such as Stan Kenton and Count Basie, Duke Ellington remains my favourite by a long way simply because of the breadth of his imagination and creativity - this music swings extremely hard, but it is also sometimes tender, melancholic and playful - he truly captures every emotion time and time again. I don't think I am exaggerating when I say that he is right up there with the greatest classical and contemporary orchestral composers of all time.