alien/ufo or area 51 fiction?

my bf wants to get into reading but he hates when a book is overly complicated and hard to read/understand (he’s dyslexic). he likes aliens and ufos or perhaps something about area 51, like some kind of horror thing or thing with creatures and whatnot. looking for a compelling fiction novel that is never boring and not too long, and with language that is simple enough to understand. please let me know if such a book exists!