For kids 10-13 (tweens)
T. A. Barron's The Merlin Effect (Arthurian-tinged middle grade with marine biology detail) is the easy recommendation. Tweens who like the Percy Jackson register will move to Barron without complaint. Richard Adams's Shardik is the harder, weirder pick for tweens who are already strong readers and want a 700-page parable about a bear god.
For teens 13-17
Sherman Alexie's The Absolutely True Diary of a Part-Time Indian is the strongest recommendation. Elizabeth George's The Edge of Nowhere is the gentler entry point. Rita Mae Brown's Rubyfruit Jungle is the right pick for older teens (16-17) who are ready for adult literary fiction with explicit content.
For teen who specifically reads fantasy
Joe Abercrombie's The Blade Itself is the right pick for 16-17 who are reading adult grimdark. Richard Adams's Shardik and The Plague Dogs both work for younger teens who want serious literary fantasy without the contemporary YA register.
For the kid who does not read
Lee Child's Make Me. Andrew Gross's 15 Seconds. Both are commercial thrillers that respect the reader and finish in a few sittings. We have given Make Me to genuinely reluctant teen readers and watched them finish in two days. The audiobook is another reliable option.
What we will not recommend
Books we have not read. Books with content the publisher's marketing has misrepresented. Books we have given to actual kids who stopped reading them on page sixty. The list is shorter than you would think.