Please help me find some gift books for my husband's upcoming birthday!

I have a very good idea of what his taste is, but since it's so different from mine, I wanted to reach out to other people to see if they have any ideas.

He tends to really enjoy books with a philosophical bent and possibly morally gray characters, and if there is humor, he prefers dry/dark humor.

Most recently, he has discovered and enjoyed the authors Otessa Moshfegh (he particularly enjoyed, and most recently read, Lapvona, and also bought himself My Year of Rest and Relaxation and McGlue by her to read) and Sayaka Murata (he liked Earthlings, and bought himself Convenience Store Woman to read).

Other books he has enjoyed:

1. He *loved* Speaker for the Dead by Orson Scott Card (even though he'd enjoyed Ender's Game, he far preferred SftD)--he loved the description of a civilization far different from our own and the philosophical musings

2. He enjoyed Invisible Man by Ralph Ellison.

3. Perfume: Story of a Murderer by Patrick Suskind is one of his all-time favorite books. He used to be a big Nirvana fan and first picked this up as it was Kurt Cobain's favorite novel, but he loved the lush description of scents in it and the moral gray.

4. One of his recent huge favorites, after which he told me he really wished he could find a book that "felt" like it, was A Tale For The Time Being by Ruth Ozeki.

5. He also really loved The Three-Body Problem by Liu Cixin.

I also remember seeing Silence by Shusako Endo around the house, though he didn't specifically tell me his impressions of it.

Lastly, he's Irish, so if there were an Irish author who also fit the kind of vibe he's into, I think he'd appreciate it, though this is by no means a must-have.