Peter Singer’s 19th century

The best 19th century Philosophy books, according to Peter Singer:

"I do think the nineteenth century was a particularly fertile period for ideas, and one in which ideas were taken seriously by many people"

https://fivebooks.com/best-books/nineteenth-century-philosophy-peter-singer/

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There's a new bio of Schopenhauer just out, too:

Arthur Schopenhauer: The Life and Thought of Philosophy’s Greatest Pessimist is a wonderful book. It’s a beautifully written biography of Arthur Schopenhauer that is reminiscent in style of Sarah Bakewell’s How to Live: A Life of Montaigne. It’s highly readable and highly recommended.
https://fivebooks.com/book/arthur-schopenhauer-david-bather-woods/

And another of Kant:

In Kant: A Revolution in Thinking, even readers having no prior acquaintance with Kant’s ideas or with philosophy generally will find an adroit introduction to the Prussian polymath’s oeuvre, beginning with his political arguments, expanding to his moral theory, and finally moving to his more abstract considerations of natural science, epistemology, and metaphysics. Along the way, Kant himself emerges from beneath his famed works, revealing a magnetic personality, a clever ironist, and a man deeply engaged with his contemporary world. https://www.hup.harvard.edu/books/9780674296107