I like Schuller a lot, but go to his books less and less, as he tends to miss certain things and is not very able to integrate it all into some larger social/musical patchwork - hence his very odd interpretation of Sam Morgan in the first book, his general ignoring of the Red Nichols/Miff Mole school, or his someone homophobic put-down of high-voiced African American singers (not really understanding that the falsetto is a real part of this tradition). Per-early jazz, I would get hold of as much of Larry Gushee's work as you can (articles here and there, worth seeking out) and wait for Gushee's book on the Creole Band, which will tell us more about early jazz and it's development than anyone has told so far -
I was reading Schuller's notes to the Buster Smith reissue on Atlantic, and they epitomized Schuller's overall problem - he described Smith's current (1960s) means of earning a living, playing for a lot of dancing and in black clubs, as being such a negation of Smith's talents, missing the obvious point that this was typical of the African American scene that has nurtured the music for so many years. Better choices for jazz's early years are Sudhalter's Lost Chords (for all its foibles), Dick Hadlock's Jazz Master's of the 1920s (an absolutely great book), Humphrey Littleton's first volume, called, I think, Jazz, and, immodestly, my own book Devilin Tune, Jazz 1900-1950. Together these will give you a much more accurate picture of the early development of the music.