Start with high-confidence sci fi & fantasy art books, then narrow by subgenre or adjacent topics.
The History of Middle-earth Boxed Set
Christopher Tolkien, J.R.R. Tolkien
The Lord of the Rings Illustrated
J. R. R. Tolkien
Dungeons & Dragons Worlds & Realms
Adam Lee, Official Dungeons & Dragons Licensed
The Steampunk Tarot
Barbara Moore, Aly Fell
Codex Seraphinianus
Luigi Serafini
The World of Robert Jordan's the Wheel of Time
Robert Jordan, Teresa Patterson
A Middle-earth Traveler
John Howe
The Illustrated World of Tolkien
David Day
Ring Legends of Tolkien Deluxe Edition
Delicious in Dungeon World Guide: the Adventurer's Bible, Complete Edition
Ryoko Kui, Taylor Engel
Fourth Wing: the Official Coloring Book
Entangled, Rebecca Yarros