24 for '24 - hosted by ninahuynh

Protagonist is 24 yr old
This is one of the more difficult prompts, as you may not know the age of the characters until you read it or it's never mentioned. 

Some examples I found:
  1. Hanna Khan Carries On by Uma Jalaluddin
  2. My Year of Rest and Relaxation by Ottessa Moshfegh
  3. Grave Sight by Charlaine Harris

Here is a list that might help you in your search.
All books added
Listen for the Lie by Amy Tintera

Listen for the Lie

Amy Tintera

338 pages • digital • 2024

fiction mystery thriller dark mysterious tense fast-paced
Milk Fed by Melissa Broder

Milk Fed

Melissa Broder

6 hours, 48 minutes • audio • 2021

fiction contemporary lgbtqia+ literary romance emotional funny reflective fast-paced
The Music of Bees by Eileen Garvin

The Music of Bees

Eileen Garvin

336 pages • paperback • 2021

fiction contemporary emotional hopeful inspiring medium-paced
A Touch of Darkness by Scarlett St. Clair

A Touch of Darkness

Hades x Persephone Saga #1

Scarlett St. Clair

409 pages • digital • 2019

fiction fantasy romance adventurous dark emotional medium-paced
Lanark by Alasdair Gray

Lanark

Alasdair Gray

576 pages • hardcover • 1981

fiction classics fantasy adventurous reflective slow-paced
Trespasses by Louise Kennedy

Trespasses

Louise Kennedy

8 hours, 59 minutes • audio • 2022

fiction historical literary dark emotional sad medium-paced
Zom 100: Bucket List of the Dead, Vol. 1 by Haro Aso

Zom 100: Bucket List of the Dead, Vol. 1

Zom 100: Bucket List of the Dead #1

Haro Aso

159 pages • digital • 2019

fiction dystopian horror manga adventurous funny lighthearted slow-paced
Kitchen by Banana Yoshimoto

Kitchen

Banana Yoshimoto

160 pages • paperback • 1988

fiction lgbtqia+ literary short stories emotional reflective sad medium-paced
The Virgin Suicides by Jeffrey Eugenides

The Virgin Suicides

Jeffrey Eugenides

249 pages • paperback • 1993

fiction literary dark reflective sad slow-paced
The Alchemist by Paulo Coelho

The Alchemist

Paulo Coelho

197 pages • paperback • 1988

fiction classics fantasy literary adventurous inspiring reflective medium-paced