I came across recently an old and rather insightful Biegeleisen book-list from the old days when the business was in Boro-Park, before their move to the Lower East Side and eventual return to Boro-Park, Brooklyn. The list of over 1000 items, containing just Hebrew works of Haskalah literature, is a fascinating look in to the tastes and wide range of interests of Jews in Boro-Park of the day, something which may come as a shock to it's current inhabitants.
Much can be seen from what Mr Biegeleisen determined to be classified as Haskalah. Some of the expected authors are there, Krochmal, Sholem Aleichem, Ephraim Deinard, Bialik, Levinson but also many authors which not be expected. Some of these include R. Abraham Isaac Kook, R. Yehuda Aryeh De Modena, and R. Haim Hirschensohn. Somehow, Joseph Klasuner's book on Jesus, titled ישו הנוצרי makes a showing more than once as well.