Lucky you! Wish I was going!
I went to see them last year at LCC in Manchester and they were brilliant, the best gig Ive been to.
I personally think all there albums are good in there own way and they're all worth a listen. The first album is the one Ive listened to the least. My favourites are Colour and the Shape and In Your Honor so if I had to choose two it would be those but There is Nothing Left to Loose is also really good and so is One by One! It depends which songs of there's you like I guess but you'll prob want to buy them all after the gig anyway!!
Have a good time Im sure you will!