Two important early 20th-century abstract algebra textbooks that were superseded by van der Waerden are:
Hasse, H., 1926. Höhre Algebra.
Haupt, O., 1929, Einführung In Die Algebra, Zweiter Band - Mit Einem Anhang Von W. Krull, Akademische Verlagsgesellschaft M. B. H., Leipzig.
For an in-depth historical account of the transition from algebra to abstract algebra (including discussions of the various textbooks) see:
Leo Corry, 1996, Modern Algebra and the Rise of Mathematical Structures, Birkhäuser Verlag.