Heartstopper · S3 E7Sleuthed by @shelfsleuth
Heartstopper · S3 E7 · Isaac Henderson · Sex ed class
Isaac in sex ed: The Ethical Slut
Dossie Easton and Janet W. Hardy published the first edition in 1997 and it became the standard guide to open relationships. For a guy who has just realized he's not interested in sex, he's being very thorough about the research.
Sources: All the books Isaac reads in Heartstopper, season three, Meeghan reads · Every book that Isaac reads in Heartstopper, Kobo · Isaac's reading list in Heartstopper season 3, Nose in a Book · Every Book Isaac Reads in Heartstopper Season 3, Den of Geek · A Complete Heartstopper Book List, The Geeky Waffle