Title was a relaunch of Invincible Iron Man (2nd series), which had ended the previous month. The first 11 issues focussed on Riri Williams, rather than Tony Stark.
With what would have been #12, the title shifted to "Legacy" numbering and renumbered with #593. This began a ramp-up to what would be #600. After that landmark issue, the title was relaunched as Tony Stark: Iron Man.
Although not an immediate spinoff, Riri Williams received her own series a little over six months later, called Ironheart.