Flotsam and Jetsam began life as an extraordinary thrash band featuring some fantastic bass courtesy of Jason Newsted (whom you all know from Metallica where he didn't play anything interesting any more). Each subsequent album has seen them changing their sound quite a bit, but each release is excellent, IMO. Their new sound is incredibly unique, only having one other band, Enertia, coming close to it. It's a quite complex mix of thrash and American power, with various other influences present; it's hard to describe, best you listen for yourself. A.K.'s vocals have been a major highlight of the band (very good clean voice that does get a little high at times, but not glam-sounding). The only "off" album would be Cuatro, which is still really good, but a lot more commercial sounding than the remainder of their catalog. Most consider "Doomsday For the Deceiver" to be their best, but I personally prefer "Drift", followed closely by "When the Storm Comes Down".
After "My God", AK announced his departure from the band to pursue, of all things, a career in a country band called "The AK Corral" or some such nonsense. James Rivera filled his shoes on the subsequent tour, but now AK has returned to the band. They plan to continue to release albums and play an occasional live show, but they have expressed a lack of interest in further touring.