As you might guess, some are better than others. Unfortunately many of the authors report hearsay as if it were fact, when there is no evidence of support.
I've lived in Galveston and studied and written its history for most of my life. (My latest book, "Bill Cherry's Galveston Memories" is available here at Amazon.com)
Ellen Beasley and Stephen Fox's "Architecture Guidebook" and Howard Barnstone's "The Galveston That Was" are the only two any student will need on the subject. When it comes to the city's architecture, they are the only ones I trust for accuracy.