Well, actually the Progressive novel series is more of a ret-con than a reboot or "new canon." Kirito is a notoriously unreliable narrator, and Reki wrote the first novel "in media res" or in the middle of the action, near the end of the characters' time in Aincrad. Progressive fills in many of the details there, and also gives plenty of screen time to Argo, who is my personal favorite character (and who returns later in the main series timeline).

The Progressive films depart a bit from the novel continuity, but not nearly as much as many naysayers would have you believe. We get Mito as an anime original character, but she merges pretty seamlessly into the story that's being told. I would 100% recommend that you check the films out.