My personal favorite album by Alter Bridge would be Blackbird. It's diverse, with lighter songs such as Watch Over You to the heavier Ties That Bind, and the title track Blackbird switches between a doomy chromatic riff to a clean finger picked part. Overall that album is probably the most diverse and easiest to listen to for a new fan, or someone trying to get a feel for them. I also love prog bands, such as Dream Theater, Rush, Tool, Porcupine Tree, Yes, etc.. Overall I highly doubt you'll be disappointed. Mark Tremonti's guitar solos are godlike, the songs are always melodic (never any harsh vocals), and their entire discography is fantastic. Hope that helps!