anything by Brandon Sanderson, especially his Cosmere stuff. Light reads despite density, story gets complex under the hood once you realize what’s going on in the greater Cosmere universe glimpsed through the various book series.

I’d second all the recommendations here, but I’d also want to know what reading level you’d be interested in, and also why you haven’t ever read a book for fun before? It would be helpful to know to be able to point to books that would avoid whatever your sticking points may have been. As far as introductory fun books I’d recommend:

• The Hobbit by JRR Tolkien (Not too long, it’s a classic and is one I’ve read multiple times over the years)
• Hatchet by Gary Paulsen (While it’s a YA novel, it was very formative for me as I read it in like 3-4th grade, is basically something that could have happened in reality but is a fictional account.)
• Cradle series by Will Wight (A bit off the path from traditional fantasy, it’s more properly in the subgenre of progression fantasy, which is basically what the genre of Dragon Ball Z would be, the unifying premise of these stories is that the MC starts fairly weak and then gets stronger over the course of the series, with generally an unlimited upper cap to how powerful characters can get through various kinds of training/levelling up/finding new gear/items/spells etc)