The Heart Of Amunah by Rabbi Schmeltzer. Hashkafa books need a “hechsher”, and this one has the best endorsements I have ever seen. It’s not easy reading though. More like a English Sefer.
Anything by the saintly tzaddik, HaRav Shimshon Pincus, the Nefesh Shimshon (for example, The Gates of Emuna)
Anything by the saintly tzaddik, HaRav A. Miller zatzal (for example, The Universe Testifies)
I’ve read many of the above, and by far the best are LIVING EMUNAH, volumes one and two! They have changed my life and entire perspective on every situation that arises! I bless Rabbi Ashear…