Sefer Ochachot V'Tochachot by Rabbi Efraim Kachlon is full of Halachic incites and chidushim about Six Subjects:
1) Gehinnom According To The Ba'al Shemtov
2) Converts To Judaism
3) Proofs of Divine Torah
4) Obligation To Rebuke According To Halacha
5) Where Was God During The Holocaust
6) Merchant Cash Advance According to Halacha: Are Jews Allowed To Lend Money To Non-Jews With High Interest?