The 1923 edition of Herman Bavinck’s Beginselen der Pscychologie, edited by Valentin Hepp, can now be accessed here. Hepp praised the work as “beyond comparison” on its subject matter. The 1897 edition of Beginselen der Pscychologie has long been available on Google Books. (Links to these and other works by Herman Bavinck are provided on the bibliography page.)
Exciting news is that an English translation of Beginselen der Pscychologie is scheduled to appear in The Bavinck Review early in 2019.