The Superman collection starts right AFTER the section of the strip I have read, with the first Bizarro and first Brainiac and Kandor stories.  Those were really cool and really significantly different in details from the comic book versions.  The place where they are starting is right around the time Jerry Siegel came back and took over the writing.  I'm really looking forward to this and to the Atomic Age volume, which should cover the loooong sequence where Lois was married to Clark and still didn't know he was Superman.  I've only read bits and pieces of that.