Two important early 20th-century abstract algebra textbooks that were superseded by van der Waerden are: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.