More books:
Ready Player One, Ernest Cline -- I don't recall there being anything too problematic for a young reader in this book. Video game treasure hunt -- the Steven Spielberg movie version is coming out next month!
Summerland, Michael Chabon -- a great writer writing a kids book -- culturally diverse fantasy plus baseball
The King in the Window, Adam Gopnik -- author mostly writes adult books
Gregor the Overlander series, by Suzanne Collins -- this earlier series by the author of The Hunger Games is enjoyable, and makes moral points (against racism, against war), and ok for much younger kids than The Hunger Games
The Chronicles of Kazam trilogy starting with The Last Dragonslayer, Jasper Fforde -- another author who usually writes adult books
The Schwa Was Here, Antsy Does TIme, Neal Shusterman -- bit of magical realism, these books are addressing some interesting issues in a subtle way
No Castles Here, A.C.E. Bauer -- fantasy in a gritty urban setting but at a kid-appropriate level
Adam Canfield of the Slash, Michael Winerip -- middle school boy dealing with ethics of journalism, has a couple sequels; author is a Pulitzer Prize winning writer for the New York Times
The Boys of San Joaquin, D. James Smith -- set in the 1950s in Fresno, California, the writing style is good (and if you enjoy things like Cheaper By the Dozen, or Knucklehead: Stories of Growing Up Scieszka, you may like it); has two sequels
Ways to Live Forever, Sally Nicholls -- 11 year old with leukemia trying to fulfill his bucket list; there's a movie version (haven't seen it)
Down the Mysterly River, Bill WIllingham and Mark Buckingham -- lots of references to character types from literature, and kind of post-modern meta-fiction-y meets Hardy Boys type main character; (note that these collaborators are primarily known for their work on the Fables comics series)
--- Some more books for fun ---
Sisters Grimm series, Michael Buckley -- this series is more appealing to
boys than one might guess; the author is very funny
The Mysterious Benedict Society series
books by Roland Smith, e.g., the I.Q. series
Dark Lord series, Jamie Thomson -- a kid who's read and enjoyed Tolkien will enjoy the central conceit: it's essentially Sauron put into a young teen body. (Be aware that these books have been published under two or maybe three different sets of titles.)
H.I.V.E. (Higher Institute of Villainous Education) series, Mark Walden -- fun anti-heroes
Flawed Dogs, Berkeley Breathed -- note treats some hard topics around pet ownership, including abuse and abandonment of pets
---- Some classics
Treasure Island, Robert Louis Stevenson
Swallows and Amazons series, Arthur Ransome