Official Blu-ray releases typically include subtitles in English (SDH) , French, and Spanish.
While I cannot provide direct subtitle files or links to piracy sites, here are details regarding the official release and subtitle availability: subtitle The.Book.of.Henry.2017.720p.BluRay.x26...
'The Book of Henry' Movie Review: A Unique Kind of Terrible - Vulture subtitle The.Book.of.Henry.2017.720p.BluRay.x26...
If you are writing a "paper" or review of the film, it is worth noting its polarizing reception: subtitle The.Book.of.Henry.2017.720p.BluRay.x26...
The film was released on Blu-ray and Digital on October 3, 2017.