Looking for Classics between 1800-1980 with a psychological or philosophical focus and maintain quality throughout

Hey, I’ve been getting more into literature recently and wanted to read more classics especially. However, one issue I have is a lot of the classics I’ve read (a lot isn’t necessarily A LOT in the way a lot of veteran readers would take it, but enough for me to develop my taste a little) is that they often start relatively uninteresting and become significantly better in the second half or near the end, or they’re great in the beginning and end but have a weak middle third/part. So I was hoping to request book suggestions that keep you enthralled or at least invested/interested the entire way through, with a decent focus on psychological or philosophical themes. Psychological are slightly preferential if a book as one or not the other, but that’s only because books I’ve really enjoyed with a psychological theme tend to have characterisation more interesting to me.

I really enjoyed The Stranger, Catcher in the Rye, Flowers for Algernon, Notes from Underground and The Death of Ivan Ilyich. These are all relatively short I know but I am open for longer novels too!

Thanks in advance, and apologies if this doesn’t fit the sub requirements!