Thick Anime/ Manga Books

Post this on a anime reddit: "I currently have a love one in prison who's a fan of manga and he's been getting into it but they have a 5 book limit every 2 weeks and some omnibus collections (like attack on titan) you can't get all the omnibus collections sadly does anyone know good thick books that cover the entire story\series in just a couple books could anyone send me a list (they do not allow hardbacks used books or spiral books and only allow from amazon and booksamillion)