The best science fiction, fantasy and horror novels were picked and announced on June 25th by the Locus Science Fiction Foundation. There are lots of good possibilities for a summer read from the winners and the other nominated titles.
Science Fiction Novel - A Desolation Called Peace by Arkady Martine
Fantasy Novel - Jade Legacy by Fonda Lee (you might start with first in the series, Jade City, reviewed by me a few days ago)
Horror Novel - My Heart is a Chainsaw by Stephen Graham Jones
Young Adult Novel - Victories Greater than Death by Charlie Jane Anders
First Novel - A Master of Djinn by P. Djeli Clark (reviewed by Katie here)
Novella - Fugitive Telemetry by Martha Wells (first one in the series, All Systems Red, reviewed by me here)
Anthology - We're Here: The Best Queer Speculative Fiction 2020 edited by C. L. Clark and Charles Payseur
Collection (short story) - Even Greater Mistakes by Charlie Jane Anders
You can find a full list of the nominees here.