There's a metric shit-tonne of new additions to Truck 13 which can all be found on http://thisistruck.com/truck-festival-lineup.aspx, but here's thirteen of them picked in a fairly arbitrary fashion:

CHAD VALLEY
FISTS
FIXERS
FLOWERS OF HELL
HOLLY MIRANDA
THE KEYBOARD CHOIR
MESSAGE TO BEARS
MEURSAULT
THE RALFE BAND
SPARKY DEATHCAP
TELLISON
UNICORN KID

and last (in the Beat-Hive (which is actually a geodesic dome structure)), but by no means least:

NERVOUS TEST_PILOT

Day tickets are ABSOLUTELY available now, if that's how you roll, priced £49/£44 Saturday/Sunday respectively. Weekend tickets are £80 Saturday-Sunday, and £95 Friday-Saturday-Sunday, which includes all sorts of musical activities (including the afore-mentioned Message To Bears)