Asking here again as I've had some great suggestions in previous years!
DD is 17, reads all sorts of things, likes SFF but not exclusively (she also likes non-fiction). My dad is getting her the new Maggie Stiefvater Raven Boys book & the Rainbow Rowell Carry On sequel. Needs to be a paper book not kindle as she's not keen on e-books, and paperbacks as it/they will be stocking fillers.
Dad - 85, non-fiction, has to be on Kindle because of his eyesight, and definitely recently published as he reads a lot and widely. His interests include art, history, music, nature. To give examples, I bought him Wilding for his birthday following a recommendation on here which he liked a lot, & he's currently reading Evening in the Palace of Reason about Bach/Frederick the Great.