While studying I was trying to place the Prince2 in the context of another methodology Lean Software Development... I started Poppendieck's book on this subject, but didn't manage to finish it...because of the 'obligatory' Prince2 certification
I have the impression that Manage It falls more in the category of Lean Software Development, does it?
Yes, Manage It! is closer to Lean Software Development than it is to Prince2 or the PMI. But I do encourage you to read the Poppendieck's book, because even if you can't go lean, learning how to recognize work that adds no value is useful as a project manager.