Aside from the 2 stories about the Freeza and Cell Saga, so far it's all been an updated retelling of the original Dragon Ball (not Z, the one with Kid Goku) story modernized for newer audiences. It also has lots of references / in jokes to future events in Z and beyond.
It changes some things and abridges others, but a good read for both those who aren't and are familiar with the original Dragon Ball adventures, which were more zany and plot-driven than the more action-focused later series. Although to be fair, the second half of the original Dragon Ball does start to become tournament / fight based, which leads up to Z, where it continues with all that.