Dune | Book by Frank Herbert
Although Dune has a really compelling narrative, with a protagonist that you want to get behind, some really evil bad guys and plenty of twists and turns, it was the planet itself that kept me from putting the book down. Herbert thought through every detail, from the local population to the development of the planet’s ecology over time. Descriptions are detailed and everything ties together — it’s totally compelling.
If you’re interested in meditation and the mind, there’s also a whole layer of narrative focused on consciousness and awareness of the present moment. Tons of links to meditation that I found totally fascinating and pretty mind-bending.