The Reichert Seven Daily Exercises (Op.5) has long been one of the most useful, repected, and treasured learning methods written for the Flute. This new, easier to read edition will bring you immesurable hours of exacting and nuanced guidance.
Difficulty guide: 6-9
Difficulty level, roughly compared to ABRSM exam grades. 0 is total beginner, 9 is advanced (beyond grade 8).