Are you talking about the book Energy Work, or the NEW tutorial online?
Anyway, as Xanth said, the MAP system integrates NEW and other techniques to teach you to project, and it's a step-by step program. So if you mean the NEW tutorials, I'd say you can use it to look up stuff you may have questions about when you reach a specific part you may find difficult. So concurrently sounds good to me.
However, the book Energy Work goes beyond what you learn with NEW (more techniques, more specialization) so I'd read it after you've finished MAP, to use it for further energy body development- because projection is just one thing to do with your energy body.